There are two universities in Cambridge England. (My reference is only Wikipedia, but I trust this isn't a controversial fact.)
1. Anglia Ruskin has a list of Clubs and Societies, and there is no listing for an "Atheistic" society (or anything similar).
2. Meanwhile, the better known University of Cambridge does have a society fitting the description: Cambridge University Atheist and Agnostic Society (CUAAS)
They have recently received a number of requests about this, and they have responded:
> No, we did not invite him and this event did not happen. We've never heard of him.
It seems this claim is false.