[1] His father William Parker was excise commissioner in 1652–3, and later a physician at Margate; his mother was Judith, daughter of Roger Beckwith of Aldborough, Yorkshire.
In 1681 he was brigadier-lieutenant, in 1683 lieutenant in the Guards, in 1685 captain of horse; later in that year he was major of Lord Arran's cavalry regiment, and in 1687 lieutenant-colonel.
[3] Arrested in London in 1693 as a party to an assassination plot against William III, planned to take place in Flanders, Parker escaped.
On 11 August, Sir John Friend having bribed a warder, Parker escaped, and a reward was offered for his apprehension.
[3] In the aftermath of the Jacobite assassination plot 1696, Parker was repeatedly mentioned in the trials of Robert Charnock and Friend.