Your recollection is correct Doug, Far-Eastern nationals have been wearing face-masks in cities and other busy locations routinely for many years now. I first noticed it when I was working in Sweden for a period around twenty years ago, when a coach-load of Japanese(?) tourists were staying in my hotel, and many of them came into the restaurant wearing masks. This was in a small town near Gothenburg.

Since then I’ve noticed, on my frequent periods spent in London - business and pleasure - that they seem to have been de rigeur amongst tourists from the Far-East.