Trafalgar Square’s St Martin-in-the-Fields gives up secrets of its stones

Church marks 300 years with exhibition and online archive telling of UK's first Black voters, and history of compassion and protest

From a family of chimney sweeps including one of Britain's two earliest documented Black voters, to the mystery of a 19-year-old youth believed enslaved, St Martin-in-the-Fields church on Trafalgar Square still has secrets to share as it marks its 300th anniversary.

Standing at the heart of London's political and cultural life for three centuries, its ranks of engraved memorial stones set into the floor and walls of the crypt and cafe are yielding glimpses into long-forgotten lives of ordinary Londoners.