The GUM clinic was correct. As long as the head of his penis was covered, NO RISK.
I would advise if this happens again to stop and change condom.
Thanks so much for your feedback,
So even if there was pre cum on his shaft that entered me perhaps when the condom had fallen half way down, still there is no risk if it wasn't the head?
I'm going to, once again, agree totally with the assessment you received at the GUM clinic. These folks are professionals at assessing risks, and if you told them about the condom slipping down your partners shaft and they said "NO RISK," then THERE is your answer.