He was the second son of Edmund Beckett Denison and his wife Maria née Beverley, of Grimsthorpe, Yorkshire.
[1] With the outbreak of the Indian Rebellion of 1857, Denison was attached to the East India Company's military forces.
[2] In the same year a general election was called, and Denison was chosen in June as one of two Conservative candidates for the two-member Southern Division of the West Riding of Yorkshire.
[3] However, the Liberal Party subsequently nominated candidates, and Denison failed to be elected, finishing third in the poll.
Parliamentary boundaries had been altered by the Reform Act 1867, and he contested the new two-seat Eastern Division of the West Riding of Yorkshire.