A feature of the post-war years has been the custom of triennial missions which attempt to explain the gospel to every undergraduate. These missions can trace their history back to the visit of Dwight Moody and Ira D. Sankey in 1882, but the current model began with a 1940 mission led by Lloyd-Jones. Subsequent main speakers have included Michael Green, Dick Lucas (long-time rector of St Helen's Bishopsgate), John Stott; one of Stott's series of talks was subsequently published as "Basic Christianity", and Tim Keller.