[3] He was the second son of John Wilkinson, factor at Blackwell Hall in London for Potterton, West Riding of Yorkshire, and his wife Anne née Denison.
His mother's brother, Robert Denison (died 1782) of Ossington, Nottinghamshire, a woollen merchant in Leeds, bequeathed to him his business interests and his estates in County Durham, Lincolnshire, Nottinghamshire and Yorkshire on condition that he adopted the surname Denison; which he did on 16 April 1785.
In 1791, he got round a clause in his uncle's will, gave up business, and settled at Ossington as a country gentleman.
In 1802, he was elected MP for Colchester, Essex; a seat where "a long purse" was needed to win the support of the voters.
He was the father-in-law of Charles Manners-Sutton and the father of Viscount Ossington, who both became Speaker of the House of Commons.