Split ticketing
What it really means
Buying two or more tickets for parts of one journey (for example London–Birmingham as London–Coventry plus Coventry–Birmingham), which is sometimes much cheaper. It is legal as long as the train stops at the split station. Apps can find splits for you.
Context, tips & common mistakes
Split ticketing means buying several tickets covering legs of the same journey — say one ticket to an intermediate station and another onwards — which, thanks to quirks of rail pricing, is sometimes noticeably cheaper than a single through ticket. It is completely legal, with one rule: the train must actually call at every station where your tickets split.
You do not have to work the combinations out yourself; several well-known apps and websites automate the search and sell the bundle in one purchase, taking a cut of the saving. Two cautions: each ticket keeps its own restrictions (an Advance leg ties you to a specific train), and if you change trains mid-journey during disruption, sorting out replacement arrangements across multiple tickets takes more patience.