aerial photograph of Bolingbroke Castle in Lincolnshire England UK. Bolingbroke is an "enclosure castle", one where the primary defence is through the curtain wall and towers rather than a fortified keep. Most enclosure castles were built in the 13th Century with a few in the 14th century. Bolingbroke Castle was built in the 13th Century and is most famous as being the birthplace of Henry IV. The castle was rebuilt in the 15th century but by the outbreak of the English Civil War it was in a dilapidated state. Despite its condition, the castle was fortified and held by the Royalists until they were defeated by the Parliamentarians after a siege, following which the castle was slighted.