Duke of Northumberland’s River

The Duke of Northumberland's River, or D. O. N. River, consists of two distinct artificial watercourses in west London. Originally known as the Isleworth Mill Stream or River, this name more accurately reflects the economic motivations behind its creation. The river system includes an upper section that diverts water from the River Colne—using a sluice—and channels it through the Crane River, extending approximately 5 miles (8 km) to bypass Heathrow Airport. The lower section, about 1.8 miles (2.9 km) long, takes its flow from the Crane near Whitton, Twickenham, and directs it through Isleworth, discharging into the tidal Thames. A sluice beneath Mill Plat feeds the main lake in Syon Park.

The western section of the river was constructed during the reign of King Henry VIII to supplement the flow for existing mills and to support new ones, thereby generating revenue for the Duke of Northumberland’s estate and providing irrigation for tenant fields. The area’s thin topsoil, predominantly gravel, was often unsuitable for agriculture without such enhancements.

The Duke’s family, having held the manor of Isleworth from 1547 to 1554 and Twickenham from 1538 to 1541, and from 1594, acquired significant lands in the area. They fortified their position by acquiring and rebuilding the former monastery, now known as Syon House, which has remained their southern England residence.

In 1530, records indicate that 42 labourers were employed on a new river cut from Longford, likely the Duke of Northumberland's River. This section diverted a portion of the River Colne’s flow south and eastwards to merge with the River Crane, passing through Stanwell, Bedfont, and Feltham. Initially intended to irrigate fields and orchards, it was redirected west and south in 1944 to accommodate the construction of Heathrow Airport. The Duke of Northumberland's River and its nearby counterpart were relocated further during the Heathrow Terminal 5 development, skirting the airport’s perimeter before diverging near The Two Bridges in Bedfont. The river then flows east to join the Crane in Donkey Wood, near Baber Bridge on Hounslow Heath.

The eastern section of the river, an older construct, diverts water from the Crane in Kneller Gardens, Whitton, Twickenham. It flows north past The Stoop and Twickenham Stadium, through Isleworth, and continues to supply the ornamental ponds in Syon Park. This portion of the river, built over a century before the Duke of Northumberland inherited Syon Abbey in 1594, was instrumental in supplying water for the estate and the River Thames at Isleworth Ait.

The Duke of Northumberland's River serves as both a distributary of the Colne, a tributary of the Crane, and a distributary of the Crane and a tributary of the Thames. Despite its initial purpose, the Crane was only modestly effective in driving mills. By 1543, a new mill was constructed near the Bourne, reinforced by a newly built river from the Colne across Hounslow Heath. The mill, an appurtenance of Isleworth manor until 1876, boasted various upgrades over the centuries, including steam engines by 1845 to complement its water power. By the early 20th century, it had become one of the largest flour mills in England before its closure and subsequent demolition in 1941.