What about a Clapham to London ticket? It is the railway that allows a "break of journey" provision that seems to combine with the fact that there is direct train from Clapham that goes to London via Syon Lane.
Which rule explicitly does not allow it? ATOC says Break of Journey is not allowed on a through train if it takes a route that's not the shortest route, or a route permitted by the maps, but they have not specified where that rule is and I have not found it.
Permitted routes are:
1. Shortest route
2. Through train, as I keep saying, all the way from origin to destination
3. Mapped routes in the RG
London to Syon Lane on a London-CJ ticket is none of these.
To answer your question, the matter of breaking your journey doesn't even arise if you're not on a permitted route, because then you have no valid ticket that might, or might not, allow you to break your journey. You will be sold a ticket for what you are currently doing journey-wise, plus a PF perhaps. The ticket in your pocket is of no consequence.
ATOC does not say explicitly - that's seems to be the word you want to concentrate on - that you can't break your journey. However, and this is near as makes no difference the same thing, you have to travel all the way from A to B on the through train - where A and B are on your ticket and the train doesn't accord with 1 or 3 above. If you have to stay on the train, which you do, then you rather obviously can't break your journey.
See also Yorkie's post on Friday: "I think it's perfectly acceptable to take a Peterborough -London via Ipswich train on a Peterborough-London ticket, and break the journey in Ipswich, providing your journey is resumed on a through train (ex-Peterborough)."
I am afraid I think that is nonsense. Apart from the attempts of people trying to shoehorn meaning into a couple of phrases in the routeing guide, any sensible interpretation simply tells you that a through train is an additional concession - it avoids the daft situation of being forced to change trains when you, as it were, have stood there and watched a through train leave without you. The through-train option is about catching a particular train to complete your entire journey.
I am bemused as to how this from the RG instructions:
"Most customers wish to make journeys by through trains or by the shortest route. In both cases they will be travelling on a permitted route.... A through train is advertised in the passenger railway timetable as a direct service which offers travel between a customers origin station and final destination, as printed on the ticket for the journey being made. This route may not be a permitted route if a change of train is necessary to complete the journey."
means you can think
-- It allows any number of trains to be used between any pair of stations on the 'route' as long as they are all through trains - it obviously means one train is to be used
-- Breaking your journey doesn't involve changing trains
-- That the word 'may' somehow softens the rule: it's 'may not' rather than 'is not' because a through train might be operating over a permitted route, i.e. shortest or mapped in the RG, in which case break of journey *is* allowed - *but because it's a permitted route* and not because it's a through train.
On the other hand, I do think you can go Edinburgh to Haymarket - although it's absurd - via the Fife circle, because nowhere does it say that you have to get off the train the first time it stops there. Why do I say this? I feel the railway charges you to take you from A to B, not particularly for the distance you travel. You've just gone 'round the houses' for a nice ride and not avoided the correct fare for Lochgelly, because that's not where you're going to. Note also that the doubling back rule is only to do with mapped routes in the RG, so it doesn't apply here with regard to Haymarket.
Michael.