In message , at 16:50:04 on Wed, 24 Oct
2012, Mizter T remarked:
For weekly seasons, the OP should note a photocard is required - easily
obtained from any rail station ticket office, but if you want one you
need to give them a passport sized photo first.

And as a gesture of user-friendliness, you'll probably find the
photo-booth at Cambridge is airside of the ticket barriers.
--
Roland Perry