I took the Elizabeth line from Heathrow airport to zone 4. With a zone 1-6 travelcard. I didn’t touch out at the zone 4 station and it charged me £12. This has never happened with a travelcard before and as far as I’m aware it’s never been a requirement to touch in or out if you have a valid travelcard for the zones you’re travelling from and to. So is a zones 1-6 travel card valid to/from Heathrow Elizabeth line or does it command a premium even with a travelcard?