Leslie Forster was raised on Tyneside. His first job was as a rent collector in the economically depressed Gateshead of the 1930s. That experience, together with watching his parents care for his severely disabled brother without assistance from the state, made him a lifelong socialist and supporter of the Labour Party.
In 1939 he joined the Peace Pledge Union, the Methodist Peace Fellowship and the Fellowship of Reconciliation. Faced with conscription in World War II, he became a conscientious objector: "I am a Christian and a member of the Methodist Church. I believe that war is alien to the spirit, teaching and example of Jesus Christ."
He became a member of Friends House Quaker Meeting in 1947, where he welcomed newcomers. Gay Friends remembered him making them feel at home at a time when this could not be taken for granted.
In 1966, recalling his experiences of housing poverty, Leslie became a founding member of the Camden Community Housing Association (CHA), which came to manage 1,400 housing units, including 15 special needs projects and two hostels. In 1994 the CHA built a block of eight flats for elderly people and five for families next door to Friends House. It was named Leslie Forster House.
Leslie was circulation manager for The Friend, an independent Quaker magazine. He remained active in Quaker work until well into his nineties: he was a member of the Quaker Socialist Society and the Friends Historical Society and featured in an outreach leaflet for Quakers in Britain.