Sully is a long, narrow village, spread along the shore of the Bristol Channel between Penarth and Barry, seven miles from Cardiff. The beach at Sully is mainly rock and pebble with sand at the low water line. A unique feature is Sully Island, which is connected to the mainland by a rocky causeway which is only uncovered at low tide. The currents around the causeway are treacherous as the sea attacks the island from the Bristol Channel side.
On the opposite side of the Bristol Channel is the Somerset coastal town of Watchet and out in the Channel are the two islands of Steep Holm and Flat Holm. Steep Holm is a bird sanctuary and Flat Holm is designated as a nature reserve.
Although Sully is largely a relatively modern village, most of it's growth having taken place during the last 30 years, it has a much longer history. Sully does largely consist of modern housing developments and has a relatively modern school, but the area around the parish church of St. John the Baptist is obviously much older.
The Romans certainly passed through Sully, although they left few traces - no roads or encampments. However, a burial which included Roman coins indicates that they were an influence on the area. The Norsemen also formed settlements in the area from the first half of the 9th century. Many local place names are of Scandinavian origin and there are remains of a Danish fort or camp on Sully Island.
With the Norman conquest, Reginald de Sully obtained the Manor of Sully around 1093. Little is known of him other than that he probably came over with William the Conqueror from France and was given large estates in Devon. It has been suggested that Reginald de Sully gave his name to the parish. The present church dates from around this time and was dedicated to St. John the Baptist. The fact that the resident clergyman at Sully has always been called Rector indicates that the tithes which provided his income had never been appropriated by a monastery - he was appointed by the Bishop and the church was regarded as a parish church.
By the middle of the 13th century the de Sully family held Sully, Wenvoe and Llanmaes. Reginald built the castle at Sully which was the smallest in Glamorgan. It occupied an area behind the church of about half an acre which was until recently still called Castle Wood. Occupation of the castle ceased around the mid-14th century, probably as a result of the extinction of the de Sully family.
The manor of Sully subsequently reverted to the Crown and was sold to Sir Thomas Stradling in 1538. It remained in the Stradling family until 1738 when another Sir Thomas died unmarried. The estate was then administered by Christopher Mansel and Bussy Mansel until his death in 1780. Then, after lawsuits, a private Act of Parliament granted St. Donats and Sully to Sir John de la Fountaine Tyrwhit, whose descendants took the name of Drake. They held sully until 1811 when it was sold to Evan Thomas who lived at Old Sully House until his death in 1832.
In 1838 the estate passed into the hands of Sir Josiah John Guest of Dowlais and Merthyr Tydfil. His eldest son later became the first Lord Wimbourne of Ashby. By the early years of the 20th century, the Wimbourne estate had already begun to dispose of land in the parish, and in 1914 most of their remaining interests were sold at public auction.
In the 19th century the community was almost entirely agricultural and the population was between 150 and 200. By 1920 this had increased to 550, but in the last 40 years Sully has grown substantially and is now mainly a dormitory suburb of Cardiff with a population of around 5,000.