I assume this is not permitted, but when traveling between stations with two different route options, would you be able to change your route mid-way through your journey if you were still on both routes.
IE, for lots of cross country flows with a via London route, would you be able to travel (on the XC train) to a station which would still be on the London route and then excess (most likely a zero excess) to the more obvious direct route.
This would be most useful if a journey began before 09:30/whatever the off peak restriction for the direct route is, but arrived at the point where the route would change after 09:30, allowing earlier travel. But this is why I assume it's probably not valid, although I would like confirmation.
IE, for lots of cross country flows with a via London route, would you be able to travel (on the XC train) to a station which would still be on the London route and then excess (most likely a zero excess) to the more obvious direct route.
This would be most useful if a journey began before 09:30/whatever the off peak restriction for the direct route is, but arrived at the point where the route would change after 09:30, allowing earlier travel. But this is why I assume it's probably not valid, although I would like confirmation.