It already runs into Bucks, Berks and Essex. Postal Kent tooWhat benefit does that bring, except make travel inconvenient for passengers and increase costs for the railway.
Why should TfL have responsibility for services in rural Buckinghamshire and Oxfordshire?

This TfL stuff is stupid, the natural end of London's catchment is not zone 6 or the M25. If anything, they should take ownership of all rail in the home counties.