Denison's father William was a clothier described as "an opulent merchant at Leeds".
[2] He was successful as a lawyer, and in December 1741,[2] he was appointed to succeed Sir Francis Page on the Court of the King's Bench, taking office on 16 February 1742.
[1] He served in that capacity for over twenty-three years, under chief justices, Sir William Lee, Sir Dudley Ryder, and Lord Mansfield, resigning on 14 February 1765 on the account of poor health and failing eyesight.
[2][1] Per his instruction, Denison was buried next to admired former Chief Justice William Gascoigne; a memorial was erected in his honor with an inscription by his closest friend, Lord Mansfield.
His wife, Anne, daughter of Robert Smithson, Esq., died twenty years later, and his estate passed to his wife's grand-niece, who married Edmund the fifth son of Sir John Beckett, Bart.