I don't want to be specific about the wheres involved as this is a question of principles rather than specifics.. So it's just letters for place names. Imagine a triangle with Z at the top, G in the right bottom corner; S in the left bottom corner, and A midway along the bottom edge. You can realistically travel from A to Z either way around the triangle - A - G - Z or A - S - Z. There are various intermediate stations either way. The "normal" route is A - G - Z with regular through trains and some trains that require a change at G. The single fare for this trip is (say) £10. The other route A - S - Z always requires a change at S, takes around the same amount of time and is (according to the timetable measurements) 3/4 mile (0.75 mile) longer than via G. Just for completeness, there is an intermediate station in between A and S (let's call it P). The one way fare P to Z is more than double the A to Z fare. In fact the one way fare from the intermediate point S to Z is also more than A to Z, as is the one way fare A to S. So to the question: assuming there are no TOC-specific restrictions in play; no "via" endorsements - is there any small print, term or condition to prevent one from buying an A to Z fare for any journey from A or P or S to Z or even from A to S? Or do I understand the routing rules correctly in that, because the less obvious routing (A - S - Z) is but 3/4 mile longer than the shortest route, the fare MUST be valid and accepted, including for breaks and/or short riding.