Religion?
What's that got to do with anything?
Sir Laurence Gardner-and I'm not one of his followers or true believers-was a specialist in medieval art restoration with his own business before he became a Shapeshifting Reptile (or whatever).
It's KNOWN that the Last Supper was very badly treated, painted over and vandalized over the centuries, so that very little of the original remains.
What IS known is that there was no Magdalene depicted, no mysterious floating knife and no kangaroos a la Monty Python.
Check out the Magdalene Legacy at you local library for pix.