In 1710 the father became rector of Houghton, which he held with the chapel of Witton or Wyton All Saints, Huntingdonshire.
About then Mark Hildesley the son was sent to Charterhouse School, London, where John Jortin was a schoolfellow.
[2] Hildesley's tenure of the rectory of Holwell extended over thirty-two years (1735–67), and his work there recommended him to the notice of James Murray, 2nd Duke of Atholl, the Lord of Mann, who nominated him to the see of Sodor and Man.
at Lambeth by Archbishop Thomas Herring on 7 April 1755 he was consecrated in Whitehall Chapel on the 27th, and on 6 August following was installed in the cathedral of St. German, Peel Castle, Isle of Man.
He retained the rectory of Holwell in commendam until 1767, when he was presented by Bishop Richard Trevor to the mastership of Christ's Hospital at Sherburn, near Durham.
At first, with the support of the Society for Promoting Christian Knowledge, Hildesley printed the New Testament and the Book of Common Prayer, translated, under his direction, by the clergy of the diocese, as well as the Christian Monitor, John Lewis's Exposition of the Catechism, and Bishop Wilson's Form of Prayer for the use of the herring fishermen.
Philip Moore that "this I believe, is the only country in the world, that is ashamed of, and even inclined to extirpate, if it could, its own native tongue".
[2] Hildesley was also author of an anonymous tract, Plain Instructions for Young Persons in the Principles of the Christian Religion; in six Conferences between a Minister and his Disciple; designed for the use of the Isle and Diocese of Mann.