Splitting tickets crossing London would result in less protection for passengers. A to B with a + is counted as a through journey - rather important if it is an advance and you are delayed. A to London, Oyster single, London to B would be seen as separate trips.
@Bletchleyite is suggesting a through ticket but not including payment for the underground, which would still be seen as one journey. In any event, use of more than one ticket for a journey is permitted and as long as appropriate connections times are allowed for I can't see a big problem with this. However, I don't see it being seen as an acceptable solution by the rail industry.
I thought that journeys with a gap in them didn't count. Official walking routes, yes. Official connections such as '+' or the free cross-Glasgow bus yes, but paying separately - no. Appropriate connection times apply at stations, and for recognised links, but do they apply for random links?
There are also plenty that don't. Sutton to Haywards Heath. National Rail Enquiries suggested getting the tram between West Croydon and East Croydon and won't provide a through fare, even though one exists if you walk between the two or change at Norwood Junction.
Stockport to Rochdale is route Metrolink CITZ and so is valid on the Metrolink.
Thanks. I didn’t have time to check properly at the time. The general point I was making is that Bletchleyite’s suggestion of through tickets that don’t include the underground is perfectly feasible; analogous examples already exist.
