"Graeme Wall" wrote

And, of course, there's the District/Piccadilly line between Ealing and
Hammersmith

One that hasn't been mentioned is the DLR between Tower Gateway and
Crossharbour - partly on the 1840 brick viaduct of the Blackwall Railway and
partly on concrete viaducts 150 years newer. In its time it has seen rope,
steam, and electric traction, and part of it is, at least more or less, on
the alignment of a section of the Millwall Railway which was once
horse-worked.

Peter