The Duke of Northumberland's River or D. O. N. River consists of separate upper and lower artificial watercourses in west London, United Kingdom. The older name Isleworth Mill Stream/River more accurately describes the economic motivation behind construction. The first section draws sluice-drawn water from the Colne — a source river which has seven distributaries, many of which are man-made — today an extended distance of into the Crane; its lower section of draws water from that small river in Whitton, Twickenham and discharges it via neighbouring Isleworth, passing Mill Plat into the tidal Thames. A sluice underneath Mill Plat feeds the main lake in Syon Park.
Western section
The western section was constructed during the reign of King Henry VIII of England to augment the flow supplying existing mills and to supply new mills, a source of revenue for the Duke of Northumberland's estate and which would have the corollary benefit of irrigation for his tenants' fields. The surrounding soil is fast-draining gravel. The dukes and their Somerset-styled forebears were lords of the manor of Isleworth and Twickenham, retaining much of the dwindling agricultural land until the 20th century. The family cemented its foothold in Isleworth by acquiring a former grandiose monastery by the Thames there which had become Syon House, in 1594 and rebuilding the same, which remains the southern English home of the family. In 1530 a record lists an increase, probably temporary, of 42 labourers working on a new river cut from Longford. This section diverts a small proportion of water from the River Colne at Longford, south then eastwards to the River Crane. The shallow canal flows through the north of Stanwell, Bedfont and Feltham. For a large part of its early course, it flows alongside its younger "twin", the Longford River. The first part of this upper section passed through the hamlet of Heathrow and was diverted south in 1944 when Heathrow Airport was constructed. Both minor canals were again diverted under a scheme facilitating the construction of Heathrow Terminal 5. They skirt the western and southern perimeter of Heathrow Airport then separate at The Two Bridges, road bridges of residential, bypassed Hatton Road in Bedfont. The river is carved east to join the Crane in patchy woodland known as Donkey Wood, by Baber Bridge at the west end of Hounslow Heath.
Eastern section
This section diverts water from the Crane in Kneller Gardens, Whitton, Twickenham, towards the east then northward past The Stoop and Twickenham Stadium rugby stadia, through Isleworth, then onwards to supply the ornamental ponds in the Duke of Northumberland's estate at Syon Park. Further sluices here control the flow into the park and the Thames at Isleworth Ait. This part is the older — built in the time of Syon Abbey — over 100 years before its inheritance, in 1594, by wife of the "wizard earl", Henry Percy, 9th Earl of Northumberland, Dorothy which automatically became his own as this inheritance preceded the Married Women's Property Act 1870. The Duke of Northumberland's River can thus be described as a distributary of the Colne and a tributary of the Crane; it is also a distributary of the Crane and a tributary of the Thames.
