A scenario similar to this one did happen to me.
I had contemplated this situation since the age of thirteen and I had no doubt that if it happened I would casually say hello to Moz and have a very relaxed conversation with him. As it happens, when I did spot him, outside the Mandarin Hotel in Knightsbridge, I was delivering wine to the hotel and I was carrying a case of wine costing several thousand pounds on my shoulder. I spotted him as he was about to jump in a black cab, yelled his name then ran towards the cab, which Moz had hurriedly jumped into, no doubt alarmed at the psychotic Glaswegian with a case of wine hurrying towards him. I got to the cab just after he got in and the cabbie hurriedly locked the door, which I attempted to pull open whilst repeatedly shouting at Moz "I've got to meet you, got to shake your hand!" He looked at me rather cooly in my state of obvious agitation, then got out of the cab, shook my hand and spoke to me for a few minutes on the street. I was too stunned to say much more than "You don't know what this means to me!" over and over.
He then got back in the taxi and they drove away, whilst I stood on the street and watched them go with a huge smile on my face. And a case of very expensive wine still on my shoulder.