Bishop –elect Campbell was born in Larne in County Antrim in the Diocese of Down and Connor (Northern Ireland) in 1941. He entered the novitiate of the Augustinian Fatherrs at Clare Priory in Suffolk and completed his philosophical and theological studies at the University College in Dublin. After his solemn vows, in 1966, he was sent to Rome, to complete his License in Sacred Theology at the Pontifical Gregorian University.
He was ordained a priest on September 16, 1971 at the Austin Friars School in Carlisle in the Diocese of Lancaster. He would subsequently serve as Parochial Vicar and Teacher at St. John Stone in Woodvale, Southport from 1972 to 1975. From 1975 to 1985, he was Prior for St. Monica’s Priory in London. During this period he completed a Masters in Theology at the University of London. From 1985 to 1990, he was in Africa as a teacher of Sacred Scripture and Dean of Studies at the Augustinian community of Jos in Nigeria.
Returning to England, from 1990 to 1999 he was Prior and a teacher back at the Austin Friars School in Carlisle. From 1999 up to today he has been Prior and Pastor of the Parish of St. Augustine in the Archdiocese of Westminster, where he has also served as Episcopal Vicar for Religious.