Uxbridge High Street terminated the GWR branch line from Denham.

The Uxbridge High Street branch was so constructed that it could be extended across the High Street for connection to Uxbridge Vine Street, the terminus of the GWR branch line from West Drayton). This proposal was finally abandoned in 1914.

The line from the terminus at Uxbridge High Street met the GWR/GCR joint line at Denham West junction (towards Denham) and Denham East junction (towards West Ruislip). These two lines diverged at a Y-junction, Denham South. Services from High Street all ran via Denham West junction to Denham, with some extended to Gerrards Cross. They then ran back along the main line to Greenford junction and down the GWR branch line past Castle Bar Park to West Ealing, on the GWR main line out of Paddington. Occasional services ran to destinations further afield.

The services from Denham towards Greenford called at an extra station, South Harefield, sited at the overbridge where Harvil Road crosses the main line. A station on the Central Line extension to Denham was planned here also; this came to nothing because of the Second World War, and the later cutback of the Central Line to West Ruislip. South Harefield station site is now occupied by a skip hire company.

The curve to Denham East junction was little used and was lifted during the First World War.

• 1 May 1907 Opened for passengers
• 11 May 1914 Opened to goods traffic.
• 1 January 1917 to 30 April 1919 Service suspended.
• 25 September 1939 Passenger service ceased; the goods service survived until July 1964.