Transport for London intends to incorporate the Dudding Hill Line into a longer line called West London Orbital, which will form part of the London Overground.

The Dudding Hill Line (or Dudding Hill Loop) is a railway line in west and north-west London running from Acton to Cricklewood. It is roughly 4 miles (6.4 km) long, with a 30 miles per hour (48 km/h) speed limit, and semaphore signalling. The line has no scheduled passenger service, no stations, and is not electrified. It is lightly used by freight trains and, very occasionally, passenger charter trains.

Source: Dudding Hill line – Wikipedia.
Midland suburban lines in London – 1953 route map showing Dudding Hill line

Why Dudding Hill and not Dudden Hill?

Although railway usage is almost always “Dudding Hill Railway”, the geographical area is usually called “Dudden Hill”, and there is a London Borough of Brent electoral ward of that name. Dudden Hill is named after a Saxon settler called Dodda. The earliest known record, as Dodynghill, dates from 1544. “Dudding Hill” has been regarded historically as the more genteel spelling of the name.

Source: Dudding Hill line – Wikipedia.

Further reading

Dudding Hill line – Wikipedia

New railway line for West London proposed, on Ian Visits website (2017—includes an interesting map although proposed interchange with Jubilee line is now at Neasden, not Dollis Hill)

West London Orbital