Historically, if you bought a through ticket which needed a journey across London on the tube, the journey would be covered by the ticket. You'd usually be sold a cross-London ticket, and these would only be fulfillable as paper tickets because E-Tickets cannot be used across the London Underground network.
However, we have introduced a new setting to allow for more flexibility in this area. You can now elect to split up your journey so that the section travelling across London is unticketed if this is cheaper than a through ticket. This means that you can then make your own arrangements to travel across London and you'll have two tickets to get to the first London terminal and then back out to your destination.
For example, consider a journey from Leamington to Cambridge. The fastest route is often to go into London (on e.g. the Chiltern Main Line) and then back out (via the East Coast Main Line). With the new setting enabled, we can retail two tickets from Leamington to London Terminals and from London Terminals to Cambridge.
The added benefit from this approach is that you are much more likely to be able to have your booking fulfilled as E-Tickets, as there is no need to issue tickets valid for a tube or Elizabeth Line journey (where only magstripe tickets can be accepted at the gateline).
You will need to use contactless or an Oyster card to make your way across London, but we'll give you a full itinerary to follow and ensure that you're still given enough time to make your cross-London journey (full compliance with minimum connection times). Most customers will have a payment card or Oyster card available already, and so this approach can be much more convenient than paper tickets.
Note that if you're a railcard-holder, you'll want to use an Oyster card to take advantage of your railcard discount on TfL services during off-peak times. Railcard discounts are not available if you use contactless.
It's worth being aware of the fact that the delay compensation situation and entitlement to catch next-available-trains (if you hold an Advance ticket and miss your intended service due to a tube delay) is less clear if you decide to enable this option. Some people claim that you’re no longer covered for delays across London if you do this. We don’t agree, but it’s a grey area and it wouldn't be right if we didn't warn you first about the risk.