Not a good idea on the street though.
And that's the point. On the street was a no-no, but there was never anything wrong with smoking in uniform indoors, but now that is illegal it presents a problem to smokers.
A few years back I saw a naval Lt Cdr in uniform standing hatless on the street outside a pub in Oxford smoking. I know the law meant he had to go outside for a fag but it just looked wrong. He was wearing a sword (I think he'd been to a wedding in one of the colleges) which made it look worse for some reason.