Dominating the upper end of the High Street and located close to the Great Hall, the Westgate is one of two surviving fortified gateways in Winchester. The structure shows evidence of 12th century construction, with modifications in the 13th and late 14th centuries. The portcullis and two early gunports, for use with hand-held cannon, in the western façade were part of the later remodelling. During the 16th to 18th centuries, the Westgate was used as both a lockup prison, for the drunken and disorderly, and as a debtors' gaol. Much of the graffiti carved in the softer stone in the upper chamber of the gate, derives from this use.
On the 19th July 1760 the City Corporation of Winchester granted to Carew Gauntlett, wine merchant, a lease of 'the room or late prison in or over the gate called the West Gate of this city together with the little room or hole on the left side of the stairs going up to the said room or late prison, but the room or hole called the Dungeon is not to be included in this grant'. This heralded a new role for the Westgate, that of an entertainments room for the public house that formerly adjoined it to the north. It was the fact that the Westgate adjoined the inn and that the room over was in use that saved the Westgate when the north, south and east gates were demolished in the 18th century. These other gateways were demolished partly to aid traffic flow and partly because they were becoming unsafe, indeed it is recorded that the floor of the chamber over the Northgate collapsed during a Christening party.
In 1837, the City Corporation authorised the conversion of the first floor chamber to a muniments room for the storage of the city's archives - and it continued as such for the remainder of the century. In 1898 the archives were removed and the building was restored by the removal of lathe and plaster partitions, cupboards, shelves and other 18th and 19th century additions. The conservation work revealed medieval features of the building along with later prisoners' graffiti and on the 16th September 1898 the Westgate opened to the public as a museum.
The Westgate is still a museum and the present displays include objects from Tudor and Stuart times, the famous collection of pre-Imperial weights and measures, and a fine painted ceiling from Winchester College. The ceiling is believed to have been commissioned by John White the warden of the college from 1541 to 1554 and is accompanied by two panels from a frieze thought to have been added on the occasion of Queen Mary I marriage to Philip of Spain in Winchester in 1554.