[1][2] After the war, he read Law at King's College, Cambridge, and was called to the Bar at Lincoln's Inn in 1948.
Refusing an approach to become Treasury Devil in succession to Ashworth, he was instead appointed a Queen's Counsel in 1961, becoming the youngest QC.
Parker was Deputy Chairman of the Hertfordshire Quarter Sessions from 1969 to 1971 and a Judge of the Courts of Appeal of Jersey and Guernsey from 1974 to 1983.
[2] Parker was appointed a Justice of the High Court in 1977, receiving the customary knighthood, and was assigned to the Queen's Bench Division.
[2] Parker married Ann Elizabeth Frederika (née White) in 1948; they had one son and three daughters.