"Paul Scott" wrote

Or, the DfT have told the operators that Oyster beyond the London Fare
Zones will not be permitted, as it would impact on their preferred ITSO
product. Whereas it would actually be highly sensible to allow Oyster on
short 'cross border' dead ends. (Having said that Aylesbury may just be a
stop on a route to Milton Keynes in a few years.)

The short 'cross-border' dead-ends have already been moved into the London
Fare Zones - Caterham, Tattenham Corner, Epsom Downs, Hampton Court, and
Epping into Zone 6; and Watford and Chesham into the extended Zones.

Peter