Unless I'm very much mistaken, it was Clive D. W. Feather
), in message
who said:

But you should actually be comparing before- and after-1933, when the
system was nationalised.

New lines since 1933:

Central: all the bits east of Liverpool Street, and the West Ruislip
branch, were planned in the late 1930s and opened after WW2.


A large proportion of which ran over existing track which, funnily enough,
had been developed privately before nationalisation.


H&C: service between Aldgate East and Barking started in 1936.


Eh? That runs *entirely* over the existing network.

FFS, if that's going to be the line of logic, then TfL could introduce a
whole raft of new lines with new names, running over existing bits of the
network, and then claim expansion.


Jubilee: Baker Street to Finchley Road tunnels opened 1939 (the
private sector having failed to do anything about this bottleneck).
The line south/east of Baker Street is all 1979 or later.

Metropolitan: four-tracking north of Harrow-on-the-Hill and
electrification beyond Rickmansworth are 1960s.

Northern: the bits north of Archway were opened in the late 1930s or
early 1940s.


Over existing lines again.


Piccadilly: Heathrow extension is 1970s & 1980s.

Victoria Line: built in the 1960s.


The Vic and the Jubilee extension have been the only enhancements to the
system on a scale similar to the achievements of the 1863-1910 period.

BTN