Wallingford was a Royalist town, with a garrison established there in 1642 to prevent an advance on Oxford to the north-west. Colonel Thomas Blagge was appointed governor, and in 1643 the king instructed him to refortify the castle, inspecting the results later that year. By 1644, the surrounding Thames towns of Abingdon and Reading had fallen and Parliamentary forces unsuccessfully attacked the town and castle of Wallingford in 1645. General Thomas Fairfax placed Wallingford Castle under siege the next year; after 16 weeks, during which Oxford fell to Parliamentary forces, the castle finally surrendered in July 1646 under generous terms for the defenders. The risk of civil conflict continued, however, and Parliament decided that it was necessary to slight, or damage so as to put beyond military use, the castle in 1652, as it remained a surprisingly powerful fortress and a continuing threat should any fresh uprising occur. The castle was virtually razed to the ground in the operation, although a brick building continued to be used as a prison into the 18th century. A large house was built in the bailey in 1700, followed by a gothic mansion house on the same site in 1837. The mansion, abandoned due to rising costs, was demolished in 1972, allowing Wallingford Castle to be declared a scheduled monument as well as a Grade I listed building. The castle grounds, including the remains of St Nicholas College, two sections of castle wall and the motte hill, are now open to the public. An archaeological research project run by Leicester University conducted a sequence of excavations between 2002 and 2010, aiming to better understand the historical transition from the Anglo-Saxon town of Wallingford and the "burgh", to the period of the Norman castle. The castle's motte was investigated by the Round Mounds Project during 2015 and 2016, whose results confirmed the mounds Norman origins. The grounds - Wallingford Castle Meadows - are managed by environmental learning charity Earth Trust on behalf of South Oxfordshire District Council.