Thomasine, Lady Percival, née Thomasine Bonaventure (c. 1470 – c. 1530), was a Cornish benefactress and founder of a school.
The story is of a woman tending sheep when she was approached by a London merchant and asked whether she would care to work in his house in London. Having agreed she found herself working for him and then marrying him; and after him a second citizen of London and then a third, who had the honour of being elected Lord Mayor. This third was Sir John Percival, Lord Mayor in 1498. As his widow Thomasine, Lady Percival, devoted her considerable wealth to supporting charitable works.
The story is reported by Richard Carew in his Survey of Cornwall (1602), when writing of the parish of Week St Mary in north Cornwall. It is given fuller treatment in Davies Gilbert's Parochial History of Cornwall (1838). Both authorities state the young woman's name as Thomasine Bonaventure, though the surname might refer to her good fortune rather than her ancestors. A legacy in her will to a brother, 'John Bonaventer', suggests it was her name. Both emphasize her charm and intelligence. Thomasine was a native of Week St Mary, and is said to have paid for the repair of a bridge. There is no dispute that she founded a school and library there around 1510, which was much used by the people of Cornwall and to some extent Devon, until it was suppressed in the reign of Edward VI. A copy of her will, with which she endowed the school, was bound for a buyer overseas in 1972, when it was purchased for the British Library.
According to one account Thomasine's first husband had the name Thomas Bumsby and her second Henry Gall. William Galle, tailor, and Henry Bumpstede, mercer, described as bridge masters of London Bridge, in records, were also business partners until Bumpstede died in 1486.
On the Great Western Railway, locomotive no. 3354 (later no. 3342) of the 3300 class was named Bonaventura after Thomasine; it ran from 1900 to 1938.