The ticketing on trains in Great Britain is extremely complicated, with lots of tricks available to legally reduce your ticket costs. One of them is called hidden city ticketing, but unlike on most airlines where such practice violates the contract, it is perfectly legal to do that on most train tickets in Great Britain. Such a practice is called “break of journey”, and is allowed by default on flexible tickets unless specifically prohibited.

The following are examples I know where travellers can take advantage of. None of them require sacrificing any flexibility. The suggested ticket is valid on the usual routes of the actual journey taken, possibly plus some more.

London – Brighton

If you want to go from Victoria to Brighton and return same day, and try to buy a ticket from the ticket machine, it will charge you at least £35.80 for an off-peak day return, more during peak hours. However, you can save half of this amount on weekends by using the “ticket from other stations” feature, and choose West Hampstead instead. It costs only £17.70 for a Super Off-Peak Day Return starting there, and it is valid to start at all three West Hampstead stations (Underground, Overground, Thameslink) with unlimited breaks of journey, and to cross London once by tube from St Pancras or West Hampstead to a southern terminal, which includes Victoria (however, it is not allowed to start the tube transfer at an intermediate station, such as Oxford Circus). In addition, it is also valid on the West London Line via Kensington (Olympia) as well, undercutting the fares from all intermediate stations Brondesbury to Selhurst, which are set by Southern.

This trick works at other times, and to other locations along the Brighton main line as well, and also in the other direction as well, although the saving isn’t as huge as this, as Super Off-Peak Day Returns are not generally available on fares set by Southern in the country direction, but available on most fares set by Thameslink to the Brighton main line.

Ticket type	London Terminals to Brighton, Any Permitted	West Hampstead Stations to Brighton, Any Permitted
Super Off-Peak Day Single	not available	£17.60 (weekends)
Super Off-Peak Day Return	not available	£17.70 (weekends)
Off-Peak Day Single	£35.70 (after 09:30)	£29.00 (after 09:30)
Off-Peak Day Return	£35.80 (after 09:30)	£29.10 (after 09:30)
Anytime Day Single	£36.10	£35.00
Anytime Day Return	£40.80	£40.10
Off-Peak Return	£45.60 (after 09:30)	£42.80 (after 09:30)

If you are travelling on weekends between London and the south coast, you can save money by buying a ticket from West Hampstead instead (or some other appropriate National Rail stations north and east of it, if you require other travel in London). If you can’t see a super off-peak ticket available to your destination, you can try to buy two tickets instead, one to your final calling point on the Brighton main line (i.e. Three Bridges if travelling via Horsham to the West Coastway, Wivelsfield if travelling via Lewes to the East Coastway, or Brighton if you change there), and an off-peak ticket for the remainder of your journey.

For example, if you want to travel from London Victoria to Worthing (via Hove) and return same day on a weekend, instead of buying the offered ticket for £38.30 from a ticket machine, you can buy two tickets instead, one from West Hampstead to Hove for £17.70, and one from Hove to Worthing for £6.30, a total of £24.00.

Note that if your journey starts at one of the Thameslink core stations (St Pancras to London Bridge inclusive), there are three cheaper tickets available, including London Terminals to Brighton, route Thameslink only (not valid at St Pancras or Farringdon, with the northernmost validity being City Thameslink), London Thameslink to Brighton, route not Underground, and a named station to Brighton, route not Underground. These three tickets are priced the same at £15.50 for a Super Off-Peak Day Return, but the validity is different.

The one with the least validity is the London Terminals to Brighton, route Thameslink only. Theoretically you can travel to any of the southern terminals on any of the permitted routes, but you can only use Thameslink (the operator) but not Gatwick Express or Southern trains, which effectively limits you to one of the core stations on the Thameslink route.

The next one is a named station (such as Farringdon) to Brighton, route not Underground ticket. You can travel from the named station to Brighton on any of the permitted routes on trains of all operators (even including GWR between Redhill and Gatwick Airport!), but your journey cannot start or end north of the origin station in the ticket as it would be outside the coverage.

The ticket with the most validity among the three is the one from London Thameslink, which, by definition, includes all the stations between St Pancras and Elephant & Castle / London Bridge. Similar to the above, you can also travel on all operators. What you can do with this ticket but not the other two is, for example, start your journey from St Pancras to Brighton, and return via London Bridge and London Blackfriars to Elephant & Castle. Therefore, there is no reason at all to buy the other two tickets, as this ticket provides a superset of validity to the other two. You can also break the journey at intermediate stations such as Norwood Junction as well, where cheap tickets are not available. However, what you can’t do with this ticket is to travel from Victoria, since it is not possible to reach Victoria from the Thameslink core without using the underground. Furthermore, there is also a negative easement in the Routeing Guide which prohibits travelling via Waterloo East / Waterloo and Clapham Junction as well, but you can use a ticket from West Hampstead for such routing.

London – Blackwater Valley

The line through Blackwater Valley is called North Downs Line, which is an orbital route between Reading and Redhill but this section focuses on the route north of Guildford. From London to stations between Guildford and Reading, there are two routes available, one set by GWR intended to be used from Paddington via Reading, and another with cheaper fares set by SWR intended to be used from Waterloo (or other southern terminals) either via Staines and Wokingham, or via Surbiton and Woking / Guildford / Farnborough.

If your destination is close to Wokingham, the fastest route is usually via Reading. However, the fare set by GWR is expensive. The trick? Find an Any Permitted fare from another station with a cross-London marker, but set by SWR instead. Using a weekday off-peak journey to Crowthorne, returning same day, as an example, a ticket bought from the machine at Paddington will cost you £29.70, but if you buy a ticket from Queen’s Park instead, it will cost you just £28.40, and if you travel later in the day (from 12:01 but not the evening peak) or on a Sunday, it is even cheaper, with an Evening Out or Sunday Out ticket for just £23.10, because these fares are set by SWR (presumably by changing at Waterloo and Wokingham) despite that the fastest route (changing at Paddington and Reading) doesn’t even use any SWR services. There is also a cheaper not via London fare which can be used by changing at, for example, Willesden Junction, Richmond and Wokingham.

If you need to travel within London in addition to a return journey, a combination of a paper Zones 1-6 Travelcard for £15.90 and a boundary zone ticket for £13.20, totalling £29.10, still come out cheaper than a return ticket from London to Crowthorne, and with this combination, one the clock turns 09:30, you can travel anywhere you want in London before and after going to Crowthorne without limits, on all of trains (excluding Heathrow Express and Southeastern High Speed), metros, trams and buses, and you are free to use any of the routes via Reading, Staines, Surbiton or even Epsom with this combination.