Help needed

I caught the tail end of a program on t.v. the other week. It concerned either a member of the British Royal family or someone very close to them. I belive this happened in the 50's or 60's. This person was asked to meet with a man at an address in London to discuss UFO's. The man went to meet him and said that the man was of a strange appearance. This strange man then went on to disclose British nuclear capability secrets to the royal. The royal was privy to this information and said afterwards that he felt like the man was "reading his mind".
Anyway the royal(?) went back to Buckingham Palace and reported the matter. He then returned to the address with the police and the whole appearance of the room had changed "as if they had moved out in a hurry". The program then went on to say that until the day he died he belived that the man was an alien life form. They mentioned the man's name but I can't remember it and I am interested in reading his biography. Has anyone got an idea as to this man's name? He was described in the program as a man of unquestionable integrity.
Any help would be gratefully appreciated.

Was it Lord Mountbatten
He had a declared interest in UFO's

Could be, thanks for the reply, I will pop to the bookshop in a bit and find out.

I remember catching a little bit of this program , I think that the royal in question was Prince Philip.

Again I will check this out but I don't think that it was. I would have remembered. I'm pretty sure Prince Phillip did get a mention on the program though. Also the man in question has definately died since.

So...

Prince Philip goes to an unknown address and speaks with some MIB type. Only when he gets back to the palace does he report it. What? didn't he have any bodyguards or a security escort with him?

I can definitely smell #.

It wasn't Prince Phillip.