"tim....." wrote in message
...


Subject to the customary caveat on the source:
http://en.wikipedia.org/wiki/Roding_Valley_tube_station
"The station itself was opened as Roding Valley Halt by the London &
North Eastern Railway, successors to the GER, on 3 February 1936 ... .
The post-war extension of the Central Line meant that the LNER station
closed on 29 November 1947, and Roding Valley re-opened on 21 November
1948 as a London Underground station."

Ah, this little bit of underground history was not known to me.
This explains why so much of this 'new' line was opened so
quickly. It was just converted from an overground railway
that was already there.


Its also helps explain why there appear to be far more 'underground' lines
north of the river. It suited the mainline railways to have certain commuter
routes transferred to LT as extensions of their routes - many of the current
lines are the result of transfers from the 'mainline' railways...

Paul