Hadleigh Castle was first built by Hubert de Burgh, the 1st Earl of Kent, who was a key supporter of King John. De Burgh was given the honour of Rayleigh by John in 1215 as a reward for his services, but chose not to develop the existing "caput" of Rayleigh Castle, instead building a new fortification south of the town of Hadleigh. The exact date of construction is uncertain, but it is now believed the work was conducted early in de Burgh's tenure of the site, permission being retrospectively officially confirmed through a licence to crenellate in 1230 under Henry III.