the town developed on the river colne on land belonging to st albans abbey until the 16th century. during the 12th century a charter was granted allowing a market, and the building of st mary's church began. the town grew partly due to travellers going to berkhamsted castle and the royal palace at kings langley. a mansion was built at cassiobury in the 16th century. this was partly rebuilt in the 17th century and another country house was built at the grove.