How do you know someone is British when you are abroad?

So like most British things, there's a class element here. Working class background, area popular with the WC (e.g. parts of Spain, Prague lads trip): football shirt, short back and sides, Gymshark. If in a cold country, North Face puffer jacket. Middle-class and above background, area popular with MC+ (e.g. Nordic cities, parts of Portugal/Italy, most long haul): Lots of lots of Linen (if hot), chinos (if not), kinda looks like they fell out of a Charles Tyrwhitt if a man over 35. Also \*especially\* if they are under 40 and usually female: a RAINS backpack or bag. I see so many.