On 20 Apr, 15:40, Alistair Bell wrote:
The key anomaly is that Vauxhall is a London Terminal but is NOT a
London Group Routeing Point. It has London as a routeing point but
also has Clapham Junction. According to map OV, which controls both
flows, the only valid route from Watford Junction to London Group
Routeing Point is directly into Euston -- but from Watford to Clapham
Junction (and hence Vauxhall) map OV takes you down the West London
Line.

That's a good point.

Double however, it's clear that the shortest rail-only route to
Vauxhall is on the direct train to Clapham Junction. (But NOT via
Willesden on the Overground, which is fractionally further). Which
might make Shepherd's Bush suddenly valid, but then you'd have to
start asking hard questions like what the shortest route to Fenchurch
Street is

I don't think you can do that - it's the shortest route to a London
Terminal (ie the nearest one), with allowances for journeys through
London Bridge etc. Otherwise - as you mention - it starts getting
silly. Not that this is codified anywhere.

That wouldn't be valid anyway -- the moment you hit Farringdon you're
beyond the validity of a London Terminals ticket.

Not if you've switched to the tube at KXSP (and assuming Highbury-
Moorgate is valid, which it isn't).

U