In the October 1812 general election Sullivan, a supporter of the ruling Tory party, was simultaneously elected Member of Parliament (MP) for both Rye and Lincoln. Standing down as MP for Rye after a by-election in December 1812,[3] Sullivan continued to represent Lincoln until his death in April 1814.[4] Since he was a serving soldier, he played little part in Parliamentary business. He made no formal speeches,[5] and voted only twice – in May 1813 against the Catholic Relief Bill and in June 1813 in support of Christian missions to India as part of the Charter Bill.[2]
Sullivan served in the Coldstream Guards during the Peninsular War, becoming a company commander in September 1812.[6] As a Foot Guards captain and a lieutenant-colonel in the army, he was killed at the Battle of Bayonne, in south France, on 14 April 1814.[7]
He was succeeded as third baronet by his younger brother Charles, a Royal Naval officer who eventually became an admiral.[1]
There are memorial plaques to Sir Henry Sullivan, as well as to his father and other members of his family, in the Church of St Nicholas, Thames Ditton, Surrey.[8]