It's on the BAKERLOO Line.
The London Underground did give the East London line to the London Overground to ease its traffic.
On the London Underground map, the Circle Line is coloured yellow.
Central Line
The Circle Line Unfortunately this answer is wrong! According to Transport for London the only tube line to connect all London Underground lines is the Jubilee Line.
You need to get the Northern Line to Leicester Square and then the Piccadilly Line to London Waterloo.
Hammersmith & City line
Jubilee Line.
Hammersmith and City.
Black.
Green is the District Line
How many feet underground is the Circle Line in London, UK
Hammersmith and City