also uses an embedded-chip smartcard to get through doors and it works
in a very similar way to Oyster -- simply wave the card within a couple
of centimetres of the reader and the door opens.

I found my works ID was read "in preference" to the Oyster and caused Oyster
to throw up code 70's. The works system ignores Oyster totally. I knw TfL
have issued local authorities with library cards which have Oyster chips in
them, which can be used for travel. It might be ID cards through the back
door ... I guess it would have been kind of cool if I could get my works ID
validated for Oyster as it's one less bit of plastic to carry.

problems would be caused if I also put the Oyster into the holder for my
works ID ... and it looks like it would. Oh well, so much for that idea.
I guess my works ID is supposed to be in the works holder on show, and
common sense says the Oyster should live in the flimsy plastic wallet
separately from all my cash and credit cards ...

Cheers,
Dave