Civic Pride and Political Devotion: The Relics of Thomas Becket in Siena

Abstract

Through a survey of archival and primary source material, this article discusses the existence of St. Thomas Becket’s relics in Siena cathedral. The institution’s inventories indicate that, from 1482 until ca. 1529, the relics were housed in an ostensory kept in the sacristy. Today, this object is displayed in the Sala del Tesoro, in the Museum of the Opera del Duomo in Siena. Although the ostensory has been examined in previous scholarship concerned with mapping the cathedral’s heritage, its function as a vessel for the relics of Thomas Becket, and indeed the very presence of these relics in Siena, remain unexplored. Thus, seeking to understand the nature of Becket’s reception in Siena, I examine the whereabouts of his relics within the cathedral, to then widen the investigation to the city at large. The evidence shows that although there were no chapels, altars or churches dedicated to Thomas Becket within the city walls, Siena still engaged with Becket’s sainthood and legacy on multiple levels.

On 29 December 1170, the controversy surrounding Church and State involving Thomas Becket, the archbishop of Canterbury (1118–1170), and Henry II King of England (1133–1189), finally culminated with the former’s murder at the hand of four knights, who claimed to act at Henry II’s behest.1 In the aftermath of the event, the Roman Church immediately endorsed Becket’s status as a martyr, canonizing him only three years after his death (1173). Having died defending the interests of the Roman Church over those of the king, Becket became the official symbol of the libertas ecclesiae—the Church’s prerogative of immunity from secular jurisdiction and authority.2 The complexity of Becket’s legacy has led to extensive academic interest in the dissemination of his cult across Europe. Recent contributions, such as Marie-Pierre Gelin’s and Paul Webster’s edited volume on Becket, have addressed this very phenomenon, seeking to establish the impulse behind such a widespread circulation of the saint’s cult within those geographies connected to the Plantagenet dynasty.3 With a survey of historical and modern texts, Kay B. Slocum has demonstrated the continued engagement with and different approaches to Becket’s persona across the centuries.4 More recently, the celebrations for the 850th anniversary of Becket’s martyrdom in 2020 stimulated a renewed vitality within Becket scholarship. Despite the outbreak of the COVID-19 pandemic, causing major disruptions to customary access to libraries, archives and museums, most of these projects still came to fruition. In 2020, the British Archaeological Association released a special issue entirely dedicated to Becket, with authors examining the saint’s cult in Britain and Europe.5 A year later, the British Academy held a three-day international conference—Thomas Becket: Life, Death and Legacy—where I presented a modified version of this article. Comprising several papers delivered at this event, MDPI journals published a special issue titled St Thomas Becket in Art.6 Finally, also in 2021, the British Museum opened the exhibition Thomas Becket: Murder and the Making of a Saint.7 Although the pandemic affected the influx of visitors and capacity of the exhibition space, the public’s positive response to this event reflects how the story of Becket and his legacy continues to captivate not only academia, but also the general public.8

With regard to the Italian peninsula, scholars have examined the dissemination of the saint’s cult along the via Francigena—the main pilgrimage route that connected Canterbury to Rome—as well as those centers loyal to either the Ghibelline or Guelph factions—supporters of the Imperial party versus that of the pope.9 Three separate chapters, in the edited volume Dall’Italia a Canterbury, explore the emergence of Becket’s cult in Northern Italy, Florence, and Como.10 A map appended to this volume identifies forty Italian cities in which St. Thomas of Canterbury was the object of specific worship.11 Siena is not included in this list, nor is it ever mentioned in the wider scholarship related to Thomas Becket’s following in Italy.12 Thus, the present research contributes to this discourse by providing physical evidence for Becket’s relics in Siena, a prominent center along the via Francigena. After its notorious Ghibelline allegiance during the 1260s, Siena had transitioned into a Guelph stronghold by the fourteenth century.13 This raises questions about the site-specific meaning and reception of Becket’s cult within this city, especially considering that St. Thomas was canonized by a Sienese pope, Alexander III (reigned 1159–1181). Through a survey of the duomo’s inventories and other primary sources, this paper traces the vicissitudes of Becket’s remains within the Sienese Cathedral of Santa Maria Assunta up to the eighteenth century. This documentation shows that, from 1482 until the mid-sixteenth century, Becket’s relics were kept in a Eucharistic monstrance. After examining the metalwork collection in the Museum of the Opera del Duomo in Siena, I identified this object with an ostensory now displayed in the Sala del Tesoro. While its commission, purpose, and past have been discussed in relation to the cathedral’s artistic heritage, the primary focus of my paper is the unexplored relationship between this vessel and the relics housed therein.14 The inquiry then extends to the city as a whole, seeking to understand how Becket’s cult manifested in Siena, if at all. This entails an assessment of thirteenth-century liturgical texts, and leads to new considerations surrounding Spinello Aretino’s frescoes in the Palazzo Pubblico (c. 1408), a decorative cycle commemorating the Sienese pope Alexander III.

The earliest documentary record signaling the presence of Becket’s relics in the Sienese cathedral is the 1482 sacristy inventory, which describes them as contained in:

A silver tabernacle, circular, covered with certain gold leaf, with a silver base, with nine precious stones, with the coat of arms of the cardinal of San Marcello, to cherish the body of Christ. It housed the relics of Saint Thomas of Canterbury, it weighs five pounds and ten ounces, with a small moon inside.15

Despite this being the first mention of the relics within the cathedral inventories, the ostensory had been recorded in the previous register from 1473, but with no reference to Becket’s relics:

A tabernacle gilded with silver, to cherish the body of Christ with certain (gold) leaf and a small cross on top, with nine real precious stones, with a small moon inside, with the arms of the cardinal of San Marcello and with the arms of the Sienese cardinal Piccolomini, it weighs five pounds and six ounces, with glass and two eyes of crystal-glass.16

I propose that the 1473 and 1482 inventories refer to the same object and that the tabernacolo in question is in fact an ostensory, a multi-lobed monstrance used to showcase both the Eucharist and relics, to convey their corporeal qualities. Thanks to these inventories’ descriptions, I was able to identify the tabernacolo with an ostensory still preserved in the Sala del Tesoro, in the Museum of the Opera del Duomo in Siena (Figure 1).17 The object is made of gilded silver; it measures 56 cm in height and weighs 2.4 kg.18 The most compelling visual proof to solidify this identification is the correlation between the coats of arms in the inventories and those on the ostensory in the Sala del Tesoro.19.

The emblems described in the 1473 entry belong to two Sienese cardinals—Antonio Casini (ca. 1378–1439), created cardinal with the title of San Marcello, and Francesco Todeschini Piccolomini (1439–1503), future Pope Pius III and nephew of Pope Pius II (reigned 1458–1464). Both of their coats of arms are engraved on the vessel in the Sala del Tesoro. On the front of the monstrance, Casini’s arms are displayed on the lower base, whereas Piccolomini’s can be seen on the upper base (Figure 2). This composition is inverted on the rear of the monstrance (Figure 3).

The fact that Piccolomini’s arms were not recorded in the 1482 register does not disprove this identification, as there could be occasional omissions and inconsistencies within succeeding inventory notes. For instance, this occurred for one of the Opera’s chasubles between the 1458 and 1467 inventories. In 1458, a chasuble (pianeta) decorated with the Agnus Dei and gold brocade is described as bearing the coat of arms of Caterino di Corsino, Operaio of the Duomo from 1404 to 1420.20 In the following inventory of 1467, this object is identified by the same description, but with the omission of Caterino’s arms.21 Considering the different locations of the family emblems on the ostensory—one at the bottom and the other at the top of the base—it is easy to imagine how the scribe of the 1482 inventory recorded the first coat of arms he saw before moving onto the next object. The person composing the 1473 note was evidently more scrupulous and recorded both arms.

As for the individuals these emblems represent, Francesco Piccolomini had been made archbishop of Siena in 1460 and was the patron of several artistic enterprises in the duomo, such as the Piccolomini Altarpiece and Library.22 Antonio Casini too had been bishop of Siena (1409–1426), as well as a munificent patron to his native city, as exemplified by his testamentary donations to the cathedral’s sacristy.23 Notably, however, Piccolomini was born in 1439, the same year as Antonio Casini’s death. The joint presence of the two cardinals’ coats of arms is then explained through a letter dated 23 November 1468, which identifies the object’s patron.24 The epistle was written by Francesco Piccolomini to the authorities of the Opera of the Duomo in Siena, informing them that a new and more precious ostensory was to replace a less adequate one in the cathedral’s sacristy. The new object was to be made in Rome by a local goldsmith and financed through Antonio Casini’s testamentary bequests to the duomo of Siena. The ostensory’s visual features confirm this. Casini’s emblem functions as a homage to this cardinal, whose endowment allowed for the creation of the monstrance. Nonetheless, the predominance of Piccolomini’s involvement with the object is evident in the reiteration of the moon motif—from Piccolomini’s coat of arms—that decorates the outer circumference of the glass eye and the two friezes at the base. Both the moon motif and galero (the red broad-brimmed cardinal hat) at the head of the coat of arms would identify the patron of this work as Francesco Piccolomini, who at the time of the 1473 record had been cardinal for thirteen years.

However, the 1468 letter makes no mention of Thomas Becket’s relics. On the contrary, Piccolomini specifies how the new monstrance was to be used in procession for the celebration of the Corpus Christi.25 Nonetheless, this shows that the ostensory in the Sala del Tesoro was not made specifically to house Becket’s relics and that they were inserted subsequently, as confirmed by the 1482 inventory. The fact that the newly fabricated ostensory was chosen to house the relics of St. Thomas could be interpreted as an attempt to enhance the value of the monstrance. Concomitantly, the relocation of the relics to a new and precious vessel commissioned by Cardinal Piccolomini could also be understood as an action that reveals the elevated status conferred on the saint.

Why were these relics moved to the ostensory in the 1480s? It is at least possible to advance a hypothesis based on Siena’s long-standing antagonism with Florence. The English martyr, in fact, was the object of intense devotion in Florence. As early as 1188, Thomas Becket had become the titular saint of an altar in the church of San Donato a Torri.26 Santa Reparata, the old cathedral of Florence, possessed eight relics of the saint.27 This church also had an altar dedicated to St. Thomas, which was the site of solemn and well-documented celebrations in honor of the martyr.28 Santa Reparata even owned a now-lost antiphonary devoted entirely to Becket: De sancto Thomaso di Conturbia.29 Another altar consecrated to the English saint stood in Santa Maria Novella, and was under the jus patronatus of the Minerbetti, a Florentine family that claimed to descend from a branch of the Becket family, hence the etymology of their name ‘minor Becket.’30 Thus, the presence of St. Thomas’ relics in Siena might have played a political role in the civic competition between the two Tuscan cities. As a matter of fact, by the time that the relics were relocated in Piccolomini’s ostensory, Siena and Florence were already competing with each other to secure the relics of St. John the Baptist, as noted by Timothy B. Smith.31 During the fifteenth century, Florence started to actively pursue the relics of the Baptist, the most important patron saint of that city.32 The acquisition of the Baptist’s right arm and hand by the Sienese Commune in 1464 left Florence in a state of frustration, as demonstrated by the city’s attempts to then purchase the left arm of St. John in 1489.33 It may well be that the relocation of Becket’s relics to a prominent and precious monstrance during the 1480s was part of this narrative and served as a means to claim St. Thomas’ divine protection for the city of Siena, and therefore divert it from Florence.

Retracing the inventories after 1482, Becket’s relics are recorded within all the following registers of the sacristy until the one drawn up in ca. 1529.34 They then disappear from the following inventory of 1547, where the ostensory is still catalogued, but without any mention of Becket’s relics.35 All these registers remain vague in their descriptions and never account for what type of relics were preserved inside the monstrance.36 Due to the shape of the ostensory, it is at least possible to propose what the remnants could have been by point of comparison. For instance, the camoscio relic—a leather bandage used by St. Francis to protect his side wound, preserved in the Basilica of Assisi, is also displayed in a sunflower-shaped ostensory with a circular glass eye (Figure 4).37 The vessel’s double-sided glass window requires the relic exhibited within this space to have a flat surface. Comparing the objects’ similar size, function and shape, it seems possible that Becket’s relics in Siena might also have consisted of an assembly of fabrics, perhaps fragments of cloth stained with the saint’s blood, a common type of Becket relic.38 Supporting this proposition and offering another comparison is an inventory from Worcester cathedral dated ca. 1540, which lists amongst its possessions a monstrance containing the brains of St. Thomas.39 The reference here to a brain relic can be understood as a brain-infused cloth.

As stated above, the relics are mentioned one last time in the sacristy inventories in the ca. 1529 registry, thereby suggesting that they were relocated elsewhere between 1529 and 1547. Considering this timeline, the removal of Becket’s remains from the ostensory was perhaps engendered by the reassessment of Church policies before and during the Council of Trent (1545–1563). Because of the renewed emphasis that the council imposed on the cult of the Sacrament, it was no longer deemed appropriate for an ostensory to store anything other than the Eucharist.40 The relics’ relocation is confirmed by Francesco Bossi’s apostolic visit to the Archdiocese of Siena, which constitutes our next documentary source regarding Becket’s relics. On 5 July 1575, Bossi was visiting the cathedral’s sacristy and reported that he was shown:

[…] a silver chest made with crystals and many ornaments, and in it there were various relics of saints, wrapped in silk with inscriptions, that is to say

Relics of Saint Sebastian, with the jawbone of Saint Sebastian.

[a piece] Of garment of the Virgin Mary, and of the column where Christ was tied and of the stone of the sepulcher and relics of Saint John the Baptists.

Relics of Saint Victor Martyr

Relics of Saint Thomas of Canterbury

Relics of Saint Julian, and of the martyrdom of Sebastian,

Relics of Saint Fabian

Of garments of the Virgin

Then there were other uncertain relics and without inscription.41

From Bossi’s transcription, we learn that in 1575 St. Thomas’ relics were now kept in a silver chest, still in the sacristy. The fact that they are named is significant, as they are recorded in the company of prestigious relics such as those of St. Sebastian, the Virgin Mary, St. John the Baptist, and St. Victor—the latter being one of the city-patrons. This is supported by the sharp distinction between the attestable relics that Bossi singles out as opposed to the uncertain ones—where ‘uncertain’ (incertae) probably indicates that they were devoid of identifying labels.

The very last documentary mention we have of them is in Girolamo Gigli’s Diario Sanese, published in 1723, where the author reports how the relics of St. Thomas of Canterbury could be admired in the Chigi chapel, in the cathedral.42 This space, also known as Cappella del Voto or Cappella della Madonna delle Grazie, was under the patronage of Fabio Chigi, the seventeenth-century Sienese pope, Alexander VII (reigned 1655–1667). Unfortunately, I have been unable to confirm this mention within the duomo inventories relative to the years of the Chigi chapel’s construction (1660–1664) up until 1723, the year of Gigli’s publication.43 It should be noted, however, that in these registers, even those concerning other chapels’ entries, relics of saints are notably omitted from all such descriptions, which instead tend to focus on the textiles, metalware, sculptures, paintings, and marbles used to decorate the duomo’s chapels.44 Nonetheless, Becket’s relics are also absent from Monica Butzek’s transcription of documents surrounding the dense correspondence between Alexander VII, the operaio, the architect, and other eminent figures acting as intermediaries during the construction of the Chigi chapel.45 No mention of them is made in Richard Krautheimer’s and Roger B.S. Jones’ transcription of Fabio Chigi’s diary, although this publication does not contain the full text, preserved at the Vatican Library.46 If we were to accept Gigli’s observation, it would be tempting to interpret Fabio Chigi’s incorporation of Becket’s relics in his chapel as a means to link his papal identity to that of his predecessor Alexander III, the first Sienese pope, who canonized Thomas of Canterbury. In fact, Chigi had chosen Alexander as his pontifical name specifically to pay homage to his Sienese compatriot and spiritual forebear. Chigi also renovated the monument in honor of Alexander III in the Lateran in Rome, where the twelfth-century pope was believed to be buried.47 The inscription on this cenotaph states outright that Chigi thought of himself as “Alexander III’s successor in name and office and citizen of the same city”.48 Just before this statement, the inscription recounts Alexander III’s canonizations; the first to be mentioned is that of Thomas Becket.49

Having analyzed the vicissitudes of Becket’s relics in the duomo, we now move towards the wider civic reception of St. Thomas’ cult in Siena. Aside from those in the cathedral, other Becket relics were kept in the church of Santo Stefano in Siena. Again, we have Francesco Bossi to thank for this reference. In the apostolic visit to this church, on 15 July 1575, Bossi records that he was shown “relics of St. Thomas of Canterbury”.50 The fact that within the city walls two different institutions preserved the remains of the English saint would seem to indicate that Becket was the object of devotion in Siena. Furthermore, in the Sienese contado, the Ospedale of Santa Maria della Scala held the rights of patronage over a chapel dedicated to Becket at Casole d’Elsa.51 A final piece of evidence concerns St. Catherine of Siena, who, in fact, owned a portable altar containing a stone, stained with the blood of the Canterbury martyr.52 Indeed, St. Catherine’s own private devotion to Thomas Becket, as well as the Ospedale’s involvement with the chapel of St. Thomas in Casole, would be valuable topics to pursue in future investigations.

Within the city walls, however, there were no churches, chapels, or altars dedicated to St. Thomas of Canterbury. In all likelihood, the relics in the duomo and Santo Stefano would have been shown and celebrated for the saint’s feast day on 29 December. This is especially easy to imagine for the duomo relics kept in Piccolomini’s monstrance, which would have provided an excellent display for processions. Apart from this occasion, they would have remained in the sacristy, secluded from public worship. Nevertheless, this was standard practice in the late medieval and early modern periods. If not stored in altars, most relics in the possession of a church would have been tucked away and inaccessible to the larger public of worshippers.53 This was to ensure their conservation, prevent their theft, exposure, and loss. Such praxis can also be confirmed by Bossi’s visit to the cathedral, where he records relics as prestigious as the Virgin’s garments or the column where Christ was whipped as being kept in the sacristy, and therefore not exposed to public view. Furthermore, the relics of John the Baptist, St. Victor, and St. Sebastian, that Bossi mentions in the passage reported above, were also housed in the sacristy, when in fact each of these saints had his own dedicatory altar in the cathedral. Even the most prestigious relic in the possession of the Opera, the right arm and hand of the Baptist discussed above, was stored in the sacristy.54 Therefore, the fact that the relics of St. Thomas were kept out of sight from a wider audience should not be taken as an indication of the absence of a local devotion towards this saint.

Turning to liturgy, specifically to the Ordo Officiorum Ecclesiæ Senensis, allows us to understand how Becket’s feast day was celebrated, which in turn can offer a further insight into whether his cult had particular traction in Siena. The Ordo Officiorum is an illuminated manuscript from ca. 1215, invaluable for its description of the canonical hours and liturgy of the Sienese cathedral.55 The Ordo shows that Becket’s dies natalis (29 December) was celebrated with the reading of nine lections.56 To put this in perspective, the feasts of the city’s patrons were also commemorated with nine lections, which was the maximum number assigned to an individual recurrence. In his study of the Ordo, Edward B. Garrison observes that the most important feasts for the city were the ones listed in the three following chapters: De solemnitatibus, in quibus Antiphonas duplicamus; Quibus festis Vigiliam facimus […]; Quibus Festis ad Vesperum canitur Responsorium, & sola Major Campana Pulsator.57 St. Thomas of Canterbury’s feast is inserted within the final chapter listed by Garrison. In this section, Becket is mentioned amongst a selected group of saints “for whom we sing until vespers and keep vigil because of their privilege and merit”.58 This special distinction, along with the fact that nine lections from Becket’s life were assigned to the celebration of his dies natalis, is an indication of the feast’s significance. It should be noted, however, that in the Ordo’s description of Becket’s feast day, no mention of his relics is made. This is in contrast with the celebrations of other saints, in which relics are specified and included in the description of their respective saint’s festivities.59 This might suggest that by ca. 1215 the cathedral still did not possess Becket’s relics. If this were the case, then it could be advanced that the relics in question arrived in Siena after the translation of Thomas Becket’s body in Canterbury in 1220, which provided the occasion to collect new relics ex corpore.60 Nevertheless, I would be cautious in arguing that their absence from the Ordo constitutes indisputable proof of their arrival in the cathedral post 1215–1220.

The evidence regarding Siena’s reception of Becket’s saintly identity also extends to the visual arts, namely to Spinello Aretino’s 1408 frescoes in the Palazzo Pubblico, depicting the stories from the life of the Sienese Pope Alexander III. This narrative recounts the twelfth-century conflict between Papacy and Empire (1159–1178), culminating in the defeat of Frederick I Barbarossa (reigned 1155–1190) and the end of a twenty-year long papal schism.61 One of these scenes, which is unfortunately very damaged, shows a cleric reading aloud to the pope and cardinals gathered in council (Figure 5). At the pope’s feet lies a chest filled with bones. Stefan Weppelmann has convincingly linked this fresco to a drawing by Spinello at the Morgan Library (Figure 6).62 Even if the latter presents some variations from the fresco in Siena—notably, the drawing is bereft of the reliquary chest—the correlation between the two is confirmed by an inscription in the top right corner of the drawing that reads: “As Pope Alexander listened to the miracles of Thomas of Canterbury, he canonized him”.63 This allowed Weppelmann to identify the drawing as a preparatory sketch for the scene in the Sala della Balìa, which in turn confirms the subject matter of the fresco in Siena as the Reading of the Miracles of Thomas Becket for his Canonization.64

The specific choice of Becket’s canonization as the subject matter of this section of the cycle is supported and contextualized through the diplomatic backdrop of Spinello’s commission. During the first decade of the fifteenth century, the city of Siena was directly implicated in the efforts to resolve the Western Schism (1378–1417) and had hosted Pope Gregory XII (reigned 1406–1415) and his papal court—on two separate occasions in 1407 and 1408—during his negotiations with the antipope and rival Benedict XIII (reigned 1394–1417) residing in Avignon.65 The literature on the subject has established that Spinello’s frescoes for the Sala della Balìa draw on the historical analogies between contemporary events and the twelfth-century conflict between Church and Empire.66 Both periods were characterized by political unrest, papal schisms, and the struggle to affirm the authority of the Church over secular powers. Becket’s murder and canonization, in 1170 and 1173, respectively, turned out to be greatly beneficial to the papal cause, as the martyr quickly became the official symbol of faithfulness to the Church to the detriment of secular powers. However, while in Becket’s and Alexander III’s days Siena was a Ghibelline stronghold, by the first decade of the fifteenth century, the city had become officially Guelph in sympathies.67 What is not mentioned in the scholarship surrounding this fresco is that the depiction of Becket’s canonization in the Sala della Balìa reinforces such a historical parallel. The Reading of the Miracles of Thomas Becket makes manifest Siena’s fifteenth-century allegiance to the cause of a universal Church against the threat of contemporary secular rulers, such as Ladislaus King of Naples (1377–1414), to the reunification of Christendom under one pontiff.68 The fact that in Italy Thomas Becket continued to be an inspirational patron saint for those oppressed by secular powers even during the fifteenth and into sixteenth centuries is evidenced, for instance, with Bishop Giovanni Pietro Arrivabene’s burial chapel in Urbino’s cathedral. Robert G. La France has shown that, in the altarpiece for his chapel, Arrivabene (1439–1504) chose St. Thomas Becket and St. Martin as his saintly intercessors to declare his political condemnation of Cesare Borgia’s attempt to subjugate Urbino and abuse of the Church’s resources to create a secular state in Central Italy; notably, Cesare Borgia (1475–1507) was the son of Pope Alexander VI (reigned 1492–1503).69 Once again, Thomas Becket is here depicted to remind posterity of Arrivabene’s loyalty to the Roman Church and his defiance of secular oppressors.70 Therefore, considering Becket’s politically charged sainthood, as well as the presence of Becket’s relics in Siena—virtually uncharted until now—there is no doubt that the subject of Spinello’s fresco is indeed the canonization of Thomas Becket and that this scene, along with the wider pictorial cycle in the Sala della Balìa, conveyed Siena’s political stance during the first turbulent years of the fifteenth century.

To conclude, St. Thomas of Canterbury received enough recognition in Siena for his feast day to be listed amongst the important festivities celebrated in the cathedral. However, it seems that within the city his cult never took root strongly enough to allow for his dedication to an altar, chapel, or church. Still, the presence of his relics in Siena along with Spinello’s frescoes in the Sala della Balìa confirm how the city engaged with St. Thomas’ legacy on different levels. On the one hand, the inclusion of the Reading of the Miracles of Thomas Becket in Spinello’s fresco cycle proclaims Siena’s Guelph allegiance and participation in the effort to reunite the Western Church during the first decade of the fifteenth century. On the other, the new prominence given to Becket’s relics following their relocation to the newly fabricated ostensory in the 1480s was perhaps motivated by Siena’s ongoing competition with Florence. Finally, the examination of primary source material has brought to light the additional function of Piccolomini’s ostensory, serving as a repository for the relics of St. Thomas of Canterbury. My identification of this monstrance amongst the vast corpus of liturgical objects in the care of the Museo dell’Opera del Duomo was possible thanks to the detailed fifteenth-century inventory notes, which, even if slightly divergent, were precise enough to allow me to recognize the physical object. Once identified, the monstrance and its visual features provided further evidence that filled in the lacunae of the textual documentation, such as a parameter to understand the type of relics that could and could not be housed therein. However, many questions still remain unanswered, such as when and why Becket’s relics arrived in Siena or whether Alexander VII was indeed involved in their relocation to his Chigi chapel. It is my hope that this paper can serve as a gateway for further investigations into the cult of Thomas Becket in Siena, which in turn will contribute to an ever-more comprehensive understanding of the scope and significance of the saint’s legacy in Europe.