The Dunwich Dynamo is a 200km night ride from London to the lost city of Dunwich on the Suffolk Coast. From 1992 to 1998 it ran as commercial pay-to-enter event. In 1999 it became free -just-turn-up-and-ride. This Successful format has continued since 2000. Setting a date for an informal ‘turn-up-and-ride’ event — on the Saturday night nearest the full moon in July — preserves the most important element of the event, the company of other riders.