In message , at 21:52:21 on
Sun, 24 Jan 2010, Paul Corfield remarked:

You can get an Oyster card at an Underground Ticket Office.

But if you are arriving at (say) Kings Cross St Pancras it's worth
choosing which ticket office quite carefully (because of the queues).

The new "Northern ticket hall" (because it's to the north, not because
it serves the Northern Line) probably still has the shortest queues, and
can be found by turning right at the bottom of the stairs near the
Platform 8 buffers.
--
Roland Perry