Owing to the defeat of Bedford Castle - ruined as early as 1224 - there are no castles in Bedfordshire with any masonry remnants, if we leave out the late medieval brick ruin of Someries. Nevertheless, the county does maintain some excellent motte and bailey castles, such as Cainhoe and Yelden.
Bedford was one of the burghs carrying weapons against the Danes by King Edward the Elder, Alfred the Great's son. It is probable that this county town was saddled with a castle in next to no time subsequent to the Norman Conquest, but there is no actual evidence of one until around 1130, when Payn de Beauchamp held it. In 1138, when besieged by King Stephen, its strong keep and curtain are mentioned, the implication being that they were already of stone.
For the duration of the Magna Carta war the castle was seized by Fawkes de Breaute and became the base for that notorious baron's misdeeds against his neighbors. In 1224 he overreached himself by abducting one of the King's justiciars and holding him prisoner here. The young Henry III responded by laying siege to the castle in person, bringing with him a tall siege tower, powerful catapults and a contingent of miners to tunnel beneath the curtain.
Every obstacle was one after another battered down or undermined, and when the keep fell the garrison had to admit defeat. A number of them were hanged but De Breaute himself obtained a pardon. The King ordered the total destruction of the castle, as a result of which the walls were demolished and ditches filled in. Only the oval motte remains, near the bridge across the River Ouse, and even this has been truncated. The site, however, is freely accessible to the public and is a good stop on your castle tour.