[1] The castle site was outside the western city gate, and defended on three sides by deep trenches.

The castle was built under the stewardship of Simon de Senlis, the first Earl of Northampton, in 1084.

When the King defeated the garrison at the Battle of Northampton in 1264, the castle again reverted to the Crown.

It remained so until three years into King Edward III's reign, when Thomas Wake, who was then sheriff of Blisworth, claimed it belonged to the county under his jurisdiction.

[6] Parts of the castle were still intact until the late 19th century, when the remains were sold to a railway company.

The only remains that survived were some earth banks beside St Andrew's Road and the re-positioned postern gate, "a minor archway".

[12] Northampton Castle is the location of the death of Prince Arthur, the young nephew to King John and claimant to the throne, in Shakespeare's King John, Act IV Scene III, in which he leaps to his death from the castle walls in an escape attempt.

He was last recorded as a sixteen-year-old captive in Rouen Castle in April 1203, whereafter he was rumoured to have been killed on King John's orders.