Matt Wheeler wrote:
It is usual, these days, to have a ticket office window on the "wrong"
side of the barriers... it allows people who don't have tickets for
the journey they've just made to buy one so they can leave the
station.

That's a valid point - come to think of it, now I can remember when a
teacher of mine bought some GroupSave CDRs for herself and a sizeable
group of 6th form students (me included) in Harpenden and took us
straight to Russell Square tube station with those very tickets (without
passing through any ticket gatelines on the way of course). We had to
wait a little while while she tried to get tickets to get us through the
exit gateline.