Are the routes into Waterloo not then valid into Cannon Street via Waterloo East and London Bridge?
That's me showing my inexpert knowledge of London suburban lines — I've checked the LSE map and you're right that the routes via Clapham Junction are valid from Waterloo East to London Bridge and Cannon Street under the same principle that makes them valid from Waterloo East to Charing Cross.
Yes - I think that's right - the shortest route from Exeter St Davids to Cannon Street wholly by rail ( which leaves the SWML at Wimbledon to go via Peckham Rye ) is longer than the standard route using the walking link between Waterloo and Waterloo East - so both those routes are valid by the shortest route rule.
Tickets are issued from Exeter St Davids to London Terminals and so the shortest route rule can't be used to make a non-mapped route via Peckham Rye or Herne Hill Permitted.
The routes mentioned above both use the West of England line via Yeovil Junction ( which is also a mapped route on map LE ) - I don't think you need to go via Warminster.
Peckham Rye is a routeing point on map WC and the only map rule for Exeter Group to London Group that uses WC is WE+WC. WE and WC only overlap at Castle Cary and Westbury, and the only routes from Castle Cary/Westbury to London Group on WC are via Warminster routeing point, Salisbury, Basingstoke etc.
These are really impressive. For journeys like this just enumerating the permitted routes isn't a trivial task - combining them into a single human-readable diagram is tricker still. How long did it take you?
Working all the routes took about a week (in between real life!) iirc but it was a few months back. Making the diagram took about 15 hours using MS Paint over a few days.
Superb! Just a couple of thoughts.
1. Two routing queries - which I haven't checked:
is Bath-Westbury-Chippenham specifically permitted despite the double-back from Trowbridge?
is Yeovil Jn-London via Westbury (and Salisbury?) also permitted
2. Presentation - you could de-emphasise the Virginia Water-Clapham Jn routing by putting "Twickenham/Richmond OR Hounslow" and reducing the number of individual routes that way by half.
(You could do similar with Weston SM, but I'm not sure that's so important.)
1.1 The nuance here is that it doesn't require doubling back
on the map, as map GW is drawn not to show the double-back. The routeing maps connect up the routeing points (and a few interchange points added to avoid irregularities) with straight lines. As you can trace the route on the map without doubling back, I would interpret it as a Permitted Route. Not like anyone would ever want to do it in real life anyway, though. Edit: as
JB_B points out, the reason why it's drawn that way on the map is that Trowbridge is part of Westbury Station Group, so it's allowed under the group stations rule.
1.2 Not that I saw on the maps, could you let me know where to look?
2. I think I wanted the 'neatness' of having precisely one line for each route, but that's probably a shout for making it more human-readable.
