The Cassiobury Estate also included a dower house, "Little Cassiobury" which has also survived to the present day. It may have been designed by Lady Elizabeth Wilbraham (the first woman architect), and is estimated to have been built in 1690. Under the supervision of the Portmeirion architect Clough Williams-Ellis there were renovations and extensions to the house in 1937–38. Soon after that Hertfordshire County Council bought Little Cassiobury in 1939 under a compulsory purchase order. They used part of its land to build Watford College and the house was used as an education office for most of the 20th century. Now vacant, Little Cassiobury is listed as "grade II*" and, due to its deteriorating condition, is classed as "at risk" by the English Heritage Buildings at Risk Register.