The building dates from around 1511 when it was built as a residence for Edward Stafford the 3rd Duke of Buckingham (1478-1521). It is not a castle in the military sense but an example of a Tudor era country house at a time when the countryside was increasingly peaceful.
Unfortunately for him, the 3rd Duke was beheaded for treason by Henry VIII in 1521. Following the execution Henry VIII confiscated the property and actually spent ten days there in 1535 with Queen Anne Boleyn. Later, in 1554, Queen Mary granted the property to Henry Stafford, 1st Baron Stafford. Following the Civil War in the 17th century the building fell into disrepair but was renovated in 1824 by the Howard family.
The main ranges of Thornbury comprise framed courts, of which the symmetrical entrance range, with central gatehouse and octagonal corner towers, survives, together with two less regular side ranges with many irregular projecting features and towers.
The building is now a Grade 1 listed building (highest heritage building ranking) and operated as a 26 room hotel and restaurant within the Relais & Châteaux group.
Within the castle grounds is a vineyard which produces a white wine that is served in the dining rooms.Grapes are harvested during September or October with all-comers welcomed to participate in the grape picking.