Dear friends in Cambridge

I got a RA offer in Cambridge University. The secrtary there told me
that they should wait for the work permit is through, and then can
draw up the contract to sign by both sides (they are applying for the
Work Permit for me now). But in other university my friend got the
similar offer, but he signed the contract firstly and then the university
applied the Work Permit for him.

So, could friends in Cambridge tell me wether the procedure in University
of Cambridge is different with other universities? Please. What was your
procedure when you got your offer in Cambridge at the beginning?

Thanks a lot.

ZY