When St Mary's Catholic Church in Clapham, south London, was formally opened and blessed in 1851, the ceremony had to take place at 5.30 a.m. in order to avoid local unrest due to “the growing influence of what was deemed the menace of Roman Popery”. In a sign of how times have changed, a former Archbishop of Canterbury was due to preach there on Wednesday. Lord Williams of Oystermouth, who stepped down in 2012, was to take part in a service organised by Churches Together in Clapham to mark Christian Unity week. He knows Clapham well, having preached at Holy Trinity, on the Common, in the 1970s. St Mary’s, which is attached to a Redemptorist monastery, features in Graham Greene’s novel The End of the Affair, where it is described as the “dark church in Park R