Henry wrote:
[W&C]
I've long thought it should be extended to Vauxhall and possibly
Clapham
Junction, to spread the load a bit. There was a discussion about that
here
a long time ago, and I've forgotten why it turned out to be a bad
idea. 
Can't see much advantage in connecting the W&C and Victoria, though...
The problem with the W&C is that, because of the short trains, it can
get horrendously overcrowded in the peaks (with queues up the ramps at
Waterloo).
This isn't too bad if everyone gets on at one end and gets off at the
other, but if you had an intermediate station, you'd be packing people
onto already full trains with very few getting off.
The only fix would be to extend the platforms at both stations to fit
proper length trains of 7 or 8 cars.