[...]
It is worth noting though that - even though your ticket is perfectly valid to exit the tube at Covent Garden or Leicester [Square] (though you may not enter at a station that isn't adjacent to a National Rail station) - the London Underground staff are very likely to say that your ticket is not valid to exit there (it will be rejected by the barriers), and that you will have to pay or go back down the escalator and continue on the tube to a National Rail station. It happens to me every time, although they do down after some arguing - but it does not make for a stress-free journey!
I do genuinely wonder whether it being "perfectly valid" is actually the case.
Yes, I do fully appreciate that the NRE information - somewhat buried away as it may be - is that a cross-London LU transfer journeys can be broken (though not resumed), but I am just a little curious as to whether that is actually written in to the agreement between RSP and LUL. It's fairly easy to imagine that such an agreement was basically inherited and carried over from the BR days.
In times past, my general feeling is that such things were a bit looser and less tightly specified that they would be today. Plus I think there would have been fewer concerns about passenger rights or notions about holding someone 'captive' by only allowing a journey between specified stations and disallowing exit at an intermediate station.
I just wonder if the
'right to break a cross-London LU journey' on an NR ticket with a Maltese cross might have been grafted on by RSP in more recent times without really consulting LUL on the matter... perhaps say in reaction to a customer query or complaint that actually managed to reach a pricing/fares manager in one of the TOCs, who regarded it as an inconsistency with broader NR / RSP ticket rules as they had developed.
In other words, maybe just maybe LUL isn't quite the big bad ogre on this issue that it is commonly portrayed to be? Just a thought.
Also, regardless of what the actual validity is or should be, my advice would be to only use NR tickets with a Maltese cross for journeys between stations on the NRE list at the top of the page here:
www.nationalrail.co.uk/times_fares/ticket_types/Travelling-to-london.aspx#travelling_connect
Furthermore, whilst I've certainly been somewhat loose / 'inventive' in my interpretation of the stipulation the cross-London Tube journey being made is
"subject to route of the through journey being made", I've only done so in terms of central London - I'd certainly advise against pushing it in terms of being 'inventive' with regards to far flung stations on the list (e.g. Upminster, Lewisham, Richmond etc).