According to the Westminster Abbey website, Thomas Thirlby has an unusual claim to fame: he was for the time the first and the only CHURCH OF ENGLAND bishop of Westminster:
Thomas Thirlby (c.1500-1570) was consecrated the first and only Bishop of the new short-lived diocese of Westminster in December 1540 (created once the Benedictine monastery of Westminster Abbey was dissolved by Henry VIII). No memorial exists for him in the Abbey but his supposed coat of arms appears in modern glass in the Chapter House (it seems that these were actually the arms of Thorley and had mistakenly been assigned to Thomas by an earlier writer). He died at Lambeth Palace on 26 August 1570 and was buried in the parish church nearby. He was born in Cambridge, a son of John, town clerk, and his wife Joan (Campion). His early patrons were said to have been Anne Boleyn's family. Some of the other posts he held were rector of Ribchester in Lancashire, chaplain to Henry VIII, archdeacon of Ely, prebendary of Salisbury cathedral, canon of St Stephen's Westminster and Dean of the Chapel Royal.
After the restoration of the Catholic Hierarchy in 1850, Westminster became the leading Catholic diocese of England and there have been many Cardinal Archbishops and many auxiliary bishops of Westminster since then.
According to his Dictionary of National Biography entry by Thompson Cooper, Bishop Thomas Thirlby was "at heart a Roman Catholic" and therefore reluctantly served Edward VI, enthusiastically served Mary I, and refused to serve Elizabeth I:
On the assembling of Queen Elizabeth's first parliament Thirlby sent his proxy, he being then absent on his embassy in France. On 17 April 1559 the bill for restoring ecclesiastical jurisdiction to the crown was committed to him and other peers. He opposed this measure on the third reading. He also dissented from the bill for uniformity of common prayer (cf. Zurich Letters, i. 20). He refused to take the oath of supremacy, and for this reason he and Archbishop Heath were deposed from their sees on 5 July 1559 at the lord-treasurer's house in Broad Street.
According to Bentham, Thirlby was a considerable benefactor to the see of Ely because by his interest he procured from the crown for himself and his successors the patronage of the prebends in the cathedral; but Dr. Cox, his immediate successor, asserted that although Thirlby received 500l. from Bishop Goodrich's executors for dilapidations, he left his houses, bridges, lodes, rivers, causeways, and banks, in great ruin and decay, and spoiled the see of a stock of one thousand marks, which his predecessors had enjoyed since the reign of Edward III. He also alleged that Thirlby never came into his diocese (Strype, Annals of the Reformation, ii. 580).
After his deprivation Thirlby had his liberty for some time, but in consequence of his persisting in preaching against the Reformation, he was on 3 June 1560 committed to the Tower, and on 25 Feb. 1560–1 he was excommunicated (Strype, ib. i. 142). In September 1563 he was removed from the Tower on account of the plague to Archbishop [Matthew] Parker's house at Beaksbourne (Parker Correspondence, pp. 122, 192, 195, 203, 215, 217). In June 1564 he was transferred to Lambeth Palace, and Parker, who is said to have treated Thirlby with great courtesy and respect, even permitted him to lodge for some time at the house of one Mrs. Blackwell in Blackfriars. He died in Lambeth Palace on 26 Aug. 1570. He was buried on the 28th in the chancel of Lambeth church, under a stone with a brief Latin inscription in brass (Stow, Survey of London, ed. Strype, App. p. 85). In making a grave for the burial of Archbishop Cornwallis in March 1783, the body of Bishop Thirlby was discovered in his coffin, in a great measure undecayed, as was the clothing. The corpse had a cap on its head and a hat under its arm (Lodge, Illustrations of British History, ed. 1838, i. 73 n.) His portrait is in the print of the delivery of the charter of Bridewell.