On 8 Nov, 12:33, (Neil Williams) wrote:
On Sat, 7 Nov 2009 20:11:50 -0000, "Paul Scott"

wrote:
The main thing that makes it difficult is deciding what to deduct on entry.
obviously a First Class 'National pre pay card' would need to hold a balance
of something over £1000 on journey commencement...

You probably wouldn't need to go that far, because mainline services
would presumably retain on-board ticket inspections, where a
non-validated card would presumably receive a penalty, payable
separately.

(By the same rules, you should charge a £150-ish deposit to anyone
buying a paper ticket at Euston to South Hampstead just in case they
go to Manchester).

It is perfectly reasonable and justified to deduct £1000 on entry, and
also to put up the cash fare for all local journeys to £1000.

The amount is irrelevant. The principle is either justified or it
isn't.