the name watford is first mentioned in an anglo-saxon charter of 1007, where "watforda" is one of the places marking the boundary of "oxanhaege". it is not mentioned in the domesday book of 1086, when this area was part of st albans' abbey's manor of cashio. in the 12th century the abbey was granted a charter allowing it to hold a market here and the building of st mary's church began. the settlement's location helped it to grow, since as well as trade along this north-south through route it possessed good communications into the vale of st albans to the east and into the chiltern hills along the valley of the river chess to the west. the town grew modestly, assisted by travellers passing through to berkhamsted castle and the royal palace at kings langley. a big house was built at cassiobury in the 16th century. this was partly rebuilt in the 17th century and another substantial house was built nearby at the grove. the houses were expanded and developed throughout the following centuries. cassiobury became the family seat of the earls of essex, and the grove the seat of the earls of clarendon.