Thomas of Lancaster's Date of Birth: 29 December 1277?

Thomas of Lancaster, earl of Lancaster and Leicester, was the grandson of Henry III of England, the nephew of Edward I, the great-nephew of Louis IX of France, the brother-in-law of Philip IV of France, and the younger half-brother of Joan I, queen-regnant of Navarre. Given his high birth and illustrious connections, it's perhaps odd that no chronicler recorded Thomas's birth, and as his uncle Edward I allowed him to come into his inheritance early, he didn't have to prove his age when he turned twenty-one and we therefore do not know his exact date of birth. In this post, I offer the evidence that we do have for the birthdate of one of the richest and most powerful Englishmen of the fourteenth century.

Thomas's father Edmund of Lancaster, second son of Henry III and Eleanor of Provence, and the only brother of Edward I, was born in January 1245. Edmund's first wife, the great heiress Aveline de Forz, died on 10 November 1274 at the age of only fifteen, and sometime in late 1275 or early 1276, Edmund married Blanche of Artois, whose father Robert (d. 1250) was the brother closest in age to Louis IX of France, and who was the widow of Enrique I, king of Navarre (d. July 1274). Here is the evidence for the birth and age of Thomas of Lancaster, their eldest son:

- The townspeople of Leicester, one of Earl Edmund's towns, gave a gift of five marks (800d) to the "messenger of the Lady Queen of Navarre after her delivery" of Thomas. This gift can only be dated to sometime during Edward I's sixth regnal year, i.e. between 20 November 1277 and 19 November 1278. [Records of the Borough of Leicester, ed. Mary Bateson, vol. 1, p. 178]

-  On 9 September 1298, Thomas's uncle Edward I allowed Thomas to have possession of the vast lands that had belonged to his late father Edmund (d. June 1296), and stated "the king has taken the homage of Thomas, whom he considers as of full age". [Calendar of Close Rolls 1296-1302, p. 174] This proves that Thomas was not yet twenty-one years old on 9 September 1298, and hence was born after 9 September 1277. Edward had ordered on 9 July 1297 that the tenants of his late brother Edmund were to do homage to Thomas, "notwithstanding that Thomas de Lancastre, son and heir of the said Edmund, is a minor in the king's custody." [Calendar of Patent Rolls 1292-1301, p. 291] 

- The inquisition post mortem of Thomas's father-in-law Henry de Lacy, earl of Lincoln, taken between 22 February and 1 March 1311, states that Thomas was then "thirty-two and more" or thirty-three years old. [Calendar of Inquisitions Post Mortem 1307-27, no. 279] This implies a date of birth around late 1277 or early 1278. Unfortunately, the inquisition post mortem of Edmund, earl of Lancaster, does not mention the age of his eldest son and heir.

'Thomas' was a highly unusual, even unprecedented, name in the English and French royal families of the thirteenth century, and I wonder if Edmund and Blanche chose their first son's name in honour of St Thomas Becket, murdered in his own cathedral on 29 December 1170, and much revered by the English royal family of the late thirteenth and early fourteenth centuries (Edward II visited Becket's shrine sixteen times in the nineteen and a half years of his reign). I also wonder, therefore, if Thomas of Lancaster was born on or around Becket's feast day, and if we might tentatively place his date of birth on or around 29 December 1277. If so, he was six years and four months older than his cousin and enemy Edward II, four years older than his wife Alice de Lacy, who was probably born on or around Christmas Day 1281, and forty-four years old when he was executed on 22 March 1322. Thomas's brother and heir Henry is usually assumed to have been born in 1280 or 1281, and their obscure youngest brother John of Lancaster was born before May 1286 when the three brothers are mentioned together on record for the first time. [CPR 1281-92, p. 243]