The original name of Blackcap appears to have been Mount Harry, while the hill now known as Mount Harry was called Lewes Beacon. The name probably indicates that it was used as a pagan shrine, or hearg, in early Saxon times, like the Harrow Hills in West Sussex and Middlesex, though the name was only recorded in 1610. Others have speculated that Mount Harry, then Mountharry, was named after King Henry III as it was here that Henry III was defeated by the troops of Simon de Montfort in 1264 at the Battle of Lewes. This seems less likely though.