I have been fortunate (?) enough to see HRH dressed in the kilt both semi-formally (tweed jacket, waistcoat & watchchain) and casually (old sweater over open-necked shirt - but NEVER with rolled/folded/scrunched down hose and boots!).

He is really relaxed in the latter and is obviously comfortable, but in the tweeds (often with striped shirt and tie more appropriate for wear with a trousered business suit) he seems to be aware that he is wearing a costume or a uniform - whenever I have seen him thus dressed, he's somewhat ill at ease and I suspect he knows his valet has slightly over-dressed him. He knows too that he has to wear what he is expected to wear in public - he actually has little 'say' in what is laid out for him each morning.

I wish I still had access to his personal staff so that I could question them on this.