In 1785 the castle was bought by the Oxford County Justices and rebuilding began under the London architect William Blackburn.[57] The wider castle site had already begun to change by the late 18th century, with New Road being built through the bailey and the last parts of the castle moat being filled in to allow the building of the new Oxford Canal terminus.[33] Building the new prison included demolishing the old chapel attached to St George's tower and repositioning part of the crypt in 1794.[3] The work was completed under Daniel Harris in 1805.[59] Harris gained a reasonable salary as the new governor and used convict labour from the prison to conduct early archaeological excavations at the castle with the help of the antiquarian Edward King.[60]