Another interesting thread. Would the OP still not be at risk if NRE changed its journey planner (which it could do at any time), ie. a screenshot essentially just shows the validity of the fare that day but doesn't necessarily provide assurance that it will still be valid tomorrow (since validities/easements etc. can be changed).
The Contract is specified at the time of purchase and remains in place for the validity of the ticket. So, for an annual there would be no need to print it each week, but for a Weekly then there could be problems.
That said, there are many of us who believe that if a route is permitted under the shortest route rule, then negative easements cannot prevent that being valid anyway.
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If your allowed to change trains there, then surely you are allowed to exit as it's a season ticket and it's valid between all points.
Not necessarily. In some cases you are allowed to double back for "interchange purposes only" (see 'Group Stations'). In this case, it's a debatable issue... I would like to say yes, but the TOCs are not going to be happy at that.
How is Headstone Lane on the WCML?
Well, I could turn that round and ask how isn't it?
NR trains can't stop at Headstone Lane.
LM trains can't, but it's still a Network Rail line with National Rail trains.
The only line that goes through Headstone Lane is the London Overground line.
I would argue the WCML is a 6-track line at this point, and I don't see how that can really be disputed. It doesn't matter that LM and LO run on different tracks, it's all the same route.
I go past Headstone Lane on my Leighton Buzzard-Harrow and Wealdstone train. The only time I go through Headstone Lane is when I get my second train from Harrow and Wealdstone to Headstone Lane.
If you take "go through" as being on a line with a platform, then I could use that argument about any station, such as Doncaster! I really don't think it matters if there are platforms at just one side of the through lines, or both sides.
IMO this is doubling back but the doubling back, but there is no rule against it in this instance. However it would be valid where shown by the National Rail journey planner anyway.