The island was formed by silt carried by the Tyburn and deposited where the river met the Thames. Silt also built up on the Thames bed, making it easy to cross here at low tide. It was the Romans who discovered the ford and built the first settlement on Thorney island - the one area of dry land in a marshy fen. They used the ford and island to link their road from Dover to another road heading north to Verulamium (St Albans).

Although it was well sited for travel, the island's marshy surroundings made it an unhealthy place to live. The Anglo-Saxon settlers who followed the Romans here found that they were liable to fall sick with diseases such as malaria. In 785, a document of King Offa refers to "the terrible place which is called Thorney island".

A church for St Peter

The story of Westminster Abbey begins in the early seventh century, when a small church dedicated to St Peter was built on the island. We do not know the name of the founder. According to Sulcard, an 11th century Westminster monk, the first church was built by a rich unnamed citizen of London.

Sulcard wrote that, on its completion, Melitus, bishop of London, came to dedicate the church. He was forestalled by St Peter himself, who came down from heaven during the night to perform the ceremony in person. Appearing on the river bank at what is now Lambeth, he persuaded a local fisherman to ferry him across to Thorney. On landing, he struck the ground twice, producing two springs of fresh water. Surrounded by a heavenly choir, St Peter then dedicated the church, and flew back to heaven.

St Peter was said to have rewarded the fisherman who ferried him by promising him a plentiful supply of salmon, so long as he never went fishing on Sundays. When Melitus arrived the next day to dedicate the church, the fisherman told him that St Peter had already been there, and showed him a salmon as proof of the saint's visit. You can still see images of salmon on the floor tiles of the abbey's chapter house, commemorating St Peter's gift.

An abbey church

At an unknown date, St Peter's was given to a community of monks. It was now the church of an abbey, meaning a monastery ruled by an abbot (father) rather than a bishop (St Paul's in London was also a monastery, but it was headed by a bishop and so called a "cathedral", from cathedra, the throne of a bishop). In time, the abbey came to be known as the West Minster (monastery) to distinguish it from St Paul's, the East Minster.

In the 950s, St Dunstan, bishop of London, refounded the abbey as a Benedictine monastery (one following the rule of St Benedict), and brought 12 Benedictine monks from Glastonbury to Westminster. Yet it remained a small and insignificant place until the 11th century.

Find out about another Anglo-Saxon monastery, Lindisfarne, and its famous Gospels here