The Missionary (1982)

In 1905, after ten years of missionary work in Africa, the Reverend Charles Fortescue (Sir Michael Palin) is recalled to England, where his Bishop gives him his new assignment, to minister to London's prostitutes. Charles hopes Deborah Fitzbanks (Phoebe Nicholls), his fiancée, will object and give him an excuse to say no to the Bishop. But she is so imperturbably innocent that she totally fails to understand what he is being asked to do, and urges him to do his best. Wealthy Lady Isabel Ames (Dame Maggie Smith) is expected to fund the work, but once she makes it clear to Charles that there will be no contribution unless he shares her bed.