He was the suffragan Bishop of Basingstoke from 1977 to 1993[2] and at the same time a Canon Residentiary of Winchester Cathedral.
Manktelow was educated at Whitgift School and Christ's College, Cambridge[3] and was made deacon at Michaelmas 1953 (20 September)[4] and ordained priest the Michaelmas following (19 September 1954) — both times by Maurice Harland, Bishop of Lincoln, at Lincoln Cathedral,[5] before a curacy at Boston, Lincolnshire, after which he was Vicar of Knaresborough.
[6] Following this he was Vicar of St. Wilfrid's Church, Harrogate[7] and then, his final appointment before his ordination to the episcopate, Rural Dean of the area.
He was consecrated a bishop on 31 March 1977, by Donald Coggan, Archbishop of Canterbury at Westminster Abbey.
[8] In retirement he served as an honorary assistant bishop in the Dioceses of Chichester and in Europe.