He and his elder brother, John, were committed to the Tower (1549-50) for implication in the Humphry Arundell rebellion in January, but were released October, 1551. He was, however, re-committed to the Tower in the same month, accused of being concerned in the Duke of Somerset's conspiracy, wherein, Bishop Pouet says, 'Arundell conspired with that ambitious and subtil Alcibiades, the Earl of Warwick, after Duke of Northumberland, to pull down the good Duke of Somerset, King Edward's uncle and protector.' But, as Mr. Doyne Bell points out, in his 'History of the Church of St. Peter ad Vincula, in the Tower,' if this be correct, it is singular that he should have been afterwards re-arrested for conspiring with Somerset against Northumberland. He was brought to trial with Sir Ralf Vane, and tried on the following day, viz., 29th January, 1551-52, when Machyn records that 'the quest qwytt ym of tresun, and cast hym of felonye, to be hanged.' Mr. Perne (probably the Prior of the Black Friars) 'was allowed to resort to Sir Thomas to instruct hym to dye well.' We read in Mr. Richard Howlett's 'Monumenta Franciscana,' that, in the 'Chronicon ab anno 1189 ad 1556, ex registro Fratrum Minorum Londoniæ,' under date 26th February, 1552, is recorded that on that day, 'the wyche was Fryday, was hongyd at Towre-hylle sir Myllys Partryge, knyghte, the wyche playd with Kynge Henry the viii^{te} at dysse for the grett belfery that stode in Powlles churche-yerde; the wyche was callyd the gret belfery; and Sir Raffe Vane, theys too ware hongyd. Also sir Myhylle Stonnappe and sir Thomas Arndelle, theys too ware be-heddyd at that same tyme. And theis iiii. Knyghtes confessyd that the war neuer gylte for soche thynges as was layd vn-to their charge, and dyde in that same oppinioun.' He was buried in the chapel of St. Peter ad Vincula, in the Tower. The Commission for seizing on the possessions in Cornwall and Devon of Sir Thomas Arundell, 'rebel and traitor,' is preserved amongst the Harleian MSS. in the British Museum (433, art. 1557); and an interesting catalogue of his plate, together with a list of that portion which was returned to his wife, Margaret, on 11th June, 1557, will be found in the Add. MSS. 5751. I think, but am by no means clear on the point, that this is the Arundell to whom Henry VIII. granted, on 6th June, 1545, Scilly, and the monastery of Tavistock, and to whom, in the same year, the King wrote a remarkable letter concerning the Papists in Cornwall, which is preserved amongst the MSS. at Westminster.