Since the fare increase, I have been capping at £16.70 whereas the Zone 1-8 cap is now £17.40. Not being able to work it out and for no reason other than sheer curiosity, I put in a FOI request to which I received the following reply:
Contactless uses the best value combination of cap and extension fare for the journeys made. Extension fares are set for each zonal combination and mode – “mode” in this context is defined by the fare for the relevant journey leg(s) being set by TfL alone, by the Train Companies, or by both. They are based on pay as you go journey fares, though there is one common extension fare for each zonal combination/mode whereas actual point-to-point fares may vary by individual journey. This common extension fare may be based on a generic notional journey which cannot be made in reality, at a lower price than any specific real journey. For your specific journey, the calculation is:
Zone 1-3 daily cap 8.70
Zone 4-8 extension fare x2 8.00
Total charged 16.70
