In reply to SATTY:
I have just found and watched one of the scenes where a character is abseiling.
He is using what looks like a grigri and is on a single rope abseiling in a standard way. Looks pretty OK to me.
If you think using a single rope, with no extra safety rope, is laughable, then you should go to Pembroke on a busy weekend and you will be able to laugh a lot!
CB.