I went to a Royal Garden Party once, admittedly more than 30 years ago. In those days, you were allowed to take your spouse and any unmarried dsughters of a certain age. Needless to say, the former had to have a new dress (and hat) and we never had any of the latter.
Because of the crowds (mainly but not exclusively senior Scottish Office civil servants) and the traffic restrictions, I had to park the car miles away. The gardens of Holyrood House were mobbed; not a snowball's chance of getting near Her Maj or any of the other royals - you had to be specially invited to form part of the exclusive circles which enveloped the principals.
Because of the crowds and the queues, you could either have a cup of tea or a wee cake; to have both demanded exceedingly sharp elbows. And there was no booze. (Who else would have an afternoon party in their garden without the offer of a glass of vino?)
So I don't envy the BNP's Nick Griffin; he is most unlikely to enjoy the occasion.