Archbishop Clarke, 70, (pictured above with the Catholic Archbishop of Armagh, Eamon Martin) has been a bishop in the Church of Ireland (part of the Anglican communion) for 23 years, after studying history and political science and gaining a PhD in church history.
He was elected as the ecclesiastical head of the Church of Ireland - Archbishop of Armagh in Northern Ireland - in October 2012.
He told the diocese: "When I became Archbishop of Armagh at the close of 2012, I made a quiet agreement with my family, a few close friends and myself that I would try to work on as Primate for five years, assuming of course that ill-health or mortality itself did not intervene."
"Coming towards the end of that five-year period, I would then review the situation with my family and, if all seemed to be working out reasonably well and I felt that I was still up for it, I would continue on for a further two years, but would not go on beyond that point. This latter moment in time has now arrived."
The Archbishop has two children and three grandchildren and his wife Linda died in 2009.
He added: "This time in Armagh has truly been a very agreeable experience for me, and for this I humbly thank God for the great privilege I was given in being appointed as Primate seven years ago and I also thank all of you, for your constant encouragement, your friendship, your prayers, your support and your patience."
Archbishop Clarke will continue to carry out all the duties of the Archbishop of Armagh and Primate until 2nd February 2020 and then the Church of Ireland House of Bishops will consider the selection of a successor.
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