The origin of the name is unknown. There is one theory that the Frays River began when a tree falling across the Colne deflected a branch of the river away from its natural and persistent channel. What seems more likely is that it is a man-made diversion of the River Colne created to power mills in the Uxbridge area. It is also sometimes known as the Uxbridge and Cowley Mill Stream, the Cowley Stream or Colham Mill Stream.
John Fray was Baron Lord Chancellor of the Exchequer in the 15 th century. He had considerable experience of rivers and mills having the commission to maintain navigation of the River Lea for about 20 years between around 1430-1440. As well as owning watermills in Essex, he had interests in many pieces of land across the country, which included a financial interest in Cowley Hall - a property in Hillingdon which adjoins the Frays River. Possibly the Frays River was originally a separate tributary rising in Harefield and that John Fray arranged for a cutting of a link from the Colne to this tributary to supply it with a portion of water from the larger river. The river Frays is fed by the River Colne at a weir near Denham Lock. It runs parallel to the Colne for around four miles before rejoining it south of West Drayton.
It has also been said that the Frays was made in the 17th century at the wish of the Lord of the Manor to serve the needs of his domain.
When the Grand Junction Canal was constructed from 1793 onwards, Frays River had some influence on the layout.
By 1641 the Frays river powered at least 5 mills. The Frays River continued to power four mills until the 19 th century. The last mill, Uxbridge Town Mill or Fountain's Mill, was in operation until after World War Two.
- WATERS, B. Thirteen rivers to the Thames.
- The Uxbridge Record, No. 71, Autumn 1998.
- Victoria County History, volume 4.