On 26 Apr 2007 03:57:22 -0700, John B wrote:

No, the answer is to sell extensions at a sensible price to people who
can show a paper travelcard at the start of their journey.

There's no reason why the £4 punishment fare should apply to people
who need an extension on a paper travelcard.

AIUI, period Travelcards from out-boundary on National Rail are valid
from z1-6, so the question doesn't arise.

Not so. They can be valid to any of the following:

Z1-6
Z2-6
Z3-6
Z4-6
Z5-6
Z6