Henry de Ardagh explained

Henry de Ardagh^[1] was appointed Dean of Armagh in 1262 and served until 1272.^[2]

References

1. http://www.ebooksread.com/authors-eng/james-b-leslie/armagh-clergy-and-parishes--being-an-account-of-the-clergy-of-the-church-of-ire-lse/page-3-armagh-clergy-and-parishes--being-an-account-of-the-clergy-of-the-church-of-ire-lse.shtml Armagh clergy and parishes : being an account of the clergy of the Church of Ireland in the Diocese of Armagh
2. http://www.stpatricks-cathedral.org/people/deans-of-armagh/ St Patrick's Cathedral, Armagh