In the 1148 survey of the Winton Domesday, entry 928 says "in the gate of King's Gate the sacristan receives 15d" (in porta de Chingeta habet sacrista xv d),[2] but the first extant mention of the church itself is in the Annales de Wintonia which record that in 1264 there was a citizens' revolt during which buildings were burned including "Kingsgate with the church of St Swithun above" (Kingate cum ecclesia Sancti Swythuni supra).

[4] According to legend, St Swithun has a special association with the English weather, a legend which dates from July 971 when the bones of the saint were moved from outside the old Saxon cathedral and brought inside the building, apparently causing a great thunderstorm: St Swithun's Day is celebrated on 15 July.

[1] The East wall niche, which today lies empty, most likely once held a statue of St Swithun, which was probably destroyed at this time.

[1] By the 17th century the church had fallen into disrepair, and had become home to one Robert Allen, the porter of Kings Gate, and his wife, "who did and doth keep swine at ye ende of the Chapell".

[8] The east window has some fragments of medieval stained glass, most likely depicting the Annunciation, which were brought in 1961 from St Peter's Church, Chesil.