"Barry Salter" wrote in message
...
Is it to identify the area the ticket was brought in for gate staff?

Yup...If you bought, for example, a Zone 2 to 6 Travelcard at
Cockfosters at the Northern end of the Piccadilly, and got to Bow Road,
in the Eastern sector, for example, in less than an hour (Piccadilly
Line to Kings Cross St Pancras, then Hammersmith & City Line) it would
raise suspicion that you had travelled via Zone 1...If, however, you
took over 2 hours, and could give a logical route (e.g. Piccadilly Line
to Finsbury Park, Victoria Line to Highbury & Islington, Silverlink to
Stratford, Docklands Light Railway to Bow Church), you'd be let through.

I read that and, whilst I understand that in terms of principle the
staff/company ought to be well within their rights, I'd be shocked if they
actually refused passage on such a basis.

Is there a chart of "minimum possible permissible journey times"? (Surely
not.)

K