The earliest account of Thornbury and the manor exists in the time of King Athelstan (A.D. 925-940), who was grandson of King Alfred the Great...
It was then owned by Aylward and, in A.D. 1020, his grandson Brictric succeeded to it. Brictric was ambassador at the Court of Baldwin, Count of Flanders, where he attracted the love of Baldwin’s daughter, Matilda. However, Brictric felt no affection for the lady and hastily returned to England. Matilda later married William the Conqueror, who seized the manor, together with other properties owned by Brictric, and gave it to his Queen. Not satisfied with this, she then had Brictric imprisoned in Winchester where, two years later, he died. Matilda died in 1083 and the manor reverted to the King. William Rufus ascended the throne in 1087 and granted Thornbury to Robert Fitzhamon as a reward for his support. It then passed through 28 generations to William Stafford Howard, Earl of Stafford, who sold it to his cousin, Thomas Howard, 8th Duke of Norfolk, in 1727, and in whose family it remained until 1959.
The 1st Duke of Buckingham was Humphrey Stafford, who succeeded to Thornbury in 1403 and who was created Duke of Buckingham in 1444 and was made a Knight of the Garter. He remained faithful to the Lancastrian cause and fell at the Battle of Northampton in 1460. Henry Stafford, 2nd Duke of Buckingham, helped place Richard III on the throne and, as a reward, was made Constable of England. In 1483 he was requested by King Richard to pay him a visit, but instead of accepting the invitation, he started to collect troops in Wales with the intention of leading them across the Severn. The uprising was unsuccessful and the Duke had to seek refuge in the house of a retainer, named Banister. A reward of £1,000 tempted Banister to betray him and the Duke was beheaded in Salisbury without trial. King Richard refused to pay the reward to Banister saying “if he could betray so good a master he would be false to all others”.
Henry Stafford was succeeded by his own son Edward Stafford as 3rd Duke of Buckingham. He was restored by Henry VII to all his father’s lands and titles and was made Constable of England and Knight of the Garter. Up to now Thornbury was just a manor but the Duke obtained a licence to castellate it and, in 1508, started to build the present castle.
When Henry VIII came to the throne, the Duke of Buckingham stood in high favour with his Royal Master. He was the most affluent and most honoured nobleman in the country - Constable of England. He was the King’s Lieutenant and commanded in his absence. He was with his Sovereign in 1513 at the Battle of the Spurs in Picardy, and in 1520 whilst on his way to France to take part in the campaign of the Field of the Cloth of Gold, he visited Tonbridge where he had a large estate and had cause to dismiss a steward called Kynvett. To avenge himself the steward passed on to Cardinal Wolsey certain indiscreet words uttered by the Duke. It is not known for certain whether Buckingham had serious thought regarding the throne, but he was the great grandson of Edward III’s youngest son, Thomas of Woodstock, and if Mary Tudor’s succession at that time was denied, he thought he stood heir to the throne. Henry VIII certainly seems to have thought there was some danger because on the Duke’s return from France he was arrested and taken to London, where he was found guilty of high treason and executed on Tower Hill.
Henry VIII appropriated the castle and, for 33 years, it remained a royal demesne; in 1533 he and Anne Boleyn spent 10 days here. Mary Tudor also spent some years here as a princess and, upon her death in 1554, she returned the castle to the descendants of the late Duke. For the next two centuries the castle was unoccupied and fell into ruin.
In the 1850s the castle became once more a family residence, being home to the Howards, then the Clifford family, Kenneth Bell MBE, The Baron and Baroness of Portlethen.