Regardless of the legality of it, it is astonishing that Charles or his advisors think that a million Euros in cash in a bag is a good thing to do... You would never do that in any business, in fact you would have a lot of questions to answer. He needs new advisors asap, and he should not be so naive.
Thats before the question of 'Why' a Qatari sheik would want to donate to Charles's charity.... and then why in cash... in reeks of buying favor and that he would think this is acceptable is mind blowing really. And this would be the next King of England....