Sub-surface tube network consists of 4 lines: Circle, District, Hammersmith & City, and Metropolitan. They were constructed by two companies: Metropolitan Railway and Metropolitan District Railway. Two railway companies both had been cooperating sometimes (during the construction of the Inner Circle - Circle Line, but they had a conflict here as well), so overall their networks are now integrated. But before the London Transport era you had some oddities, e.g. clockwise operations on the Inner Circle were done by the Metropolitan (outer rail), while anti-clockwise services by the District Railway (inner rail). (previous | next | back to album | 2020:02:12 09:03:43 | 44% of an album)