[2] Mercer was born in Bradford, Yorkshire, the son of a clergyman, and educated at Rossall School and Lincoln College, Oxford.[4] He was appointed Bishop of Tasmania in May 1902,[4] and consecrated by the Archbishop of Canterbury at St Paul's Cathedral on 13 July 1902.[6] He had received the honorary degree Doctor of Divinity (DD) from the University of Oxford the previous month.[7] An eminent Christian scholar,[8] on his return from the colonial episcopate he continued to serve the Church as a Canon Residentiary at Chester Cathedral and finally, from 1919 until his death, as Archdeacon of Macclesfield.During the First World War, he deputised for Francis Jayne, bishop of Chester, whose health was fragile, on a number of occasions.