Paul Oter wrote:

What is your source for that? Are you saying that if someone wanted to
make a day-trip from, say, Cambridge to East Croydon via King's Cross
Thameslink and travel first class all the way they couldn't use a first
class peak travelcard but would have to buy two separate first class
day returns?

Wouldn't surprise me. I don't believe there is such a thing as a First
Class 1-6 Travelcard.

Neil