Feeling a vocation to minister to the urban poor, Henson served in the East End of London and Barking before becoming chaplain of an ancient hospice in Ilford in 1895. In 1900 he was appointed to the high-profile post of vicar of St Margaret's, Westminster and canon of Westminster Abbey. While there, and as Dean of Durham (1913–18), he wrote prolifically and sometimes controversially. The Anglo-Catholic wing of the Church took exception to his liberal theological views, which some regarded as heretical, and sought unsuccessfully in 1917 to block his appointment as Bishop of Hereford.