 He was baptized in London in the Church of St Giles in the Fields, Holborn.Bertie was Member of Parliament for Lincolnshire from 1761 to 1779, became Lord Lieutenant of Lincolnshire on 12 February 1779, and was invested as Privy Counsellor on the same day.On his nephew's death on 8 July 1779, he succeeded him as 5th and last Duke of Ancaster and Kesteven and Marquess of Lindsey and as 8th Earl of Lindsey.