Does anyone know why Flitwick isn't included along with Luton, Leagrave and Harlington in the additional 2025 stations?
Because it is only as far as Luton Airport Parkway!!
All joking apart ... the boundary has to be somewhere, and I suspect the thought of trying to sort out fares further north requires more work.
In the same way that Bletchley is the boundary out of Euston, so that MKC is omitted .... that means Avanti WC doesn't get involved; omitting Luton leaves EMR out.
In much the same way, Huntington was the furthest north for the Network Card ... that way InterCity East Coast didn't have the complication of the NC fares.
It's all sort of logical, really ....