In the 19th Century, an extra storey of attic rooms was added on the north side of the Castle. The Mews (pictured), which now house the Kimbolton School Dining Hall and Music School, were built to provide stables for the Castle. On the east side, the avenue of Wellingtonias on either side of the Mall was planted.

 

During World War II, the Castle was used by the Royal Army Medical Corps. In 1950, the 10th Duke of Manchester, who was living in Kenya, sold the Castle and many of the family portraits to Kimbolton School, then housed in what is now the Preparatory School. Since that time, the State Rooms have been restored and redecorated and other parts of the Castle adapted to meet the changing needs of the School community.