Born in Carlisle, Cumbria, he was the eldest son of John Thomas (died 1747), vicar of Brampton, Cumberland, by his wife Ann, daughter of Richard Kelsick of Whitehaven, a captain in the merchant service.

[1] He became assistant master at an academy in Soho Square, and then private tutor to the younger son of Sir William Clayton, bart., whose sister he later married.

On 7 January 1766, he was instituted to the vicarage of St Bride's, Fleet Street, London, and in 1768 he became Dean of Westminster and of the Order of the Bath.

He marked his episcopacy by repairing the deanery at Rochester and rebuilding the bishop's palace at Bromley, which was in a ruinous state.

[2] She died on 7 July 1772, and on 12 January 1776 he married Elizabeth, daughter of Charles Baldwin of Munslow in Shropshire, and widow of Sir Joseph Yates, judge of the court of king's bench.