 Asgill was appointed equerry to Frederick, Duke of York in 1788; he would hold this post until his death.On 15 September 1788 he inherited the Asgill baronetcy upon the death of his father, and on 3 March 1790 he was promoted to command a company in the 1st Foot Guards, with the rank of lieutenant-colonel.On 28 August 1790 he married Jemima Sophia, sixth daughter of Admiral Sir Chaloner Ogle, 1st Baronet.