https://i.dailymail.co.uk/i/pix/2015/04/26/11/22FFD9CC000005...https://qph.fs.quoracdn.net/main-qimg-0fe4637f8d1b1f981c7786...
You'll see them at busy places like stations, shopping centres, airports, busy public squares etc. At least in London - perhaps not so much elsewhere. I guess half of it is deterrent & reassurance, and the other half if to stop any "active shooter" type things before they happen.
There is also SO15 which are the sort of para-military dedicated anti-terror type people who don't patrol but are stationed around the place and use motorbikes to cut through traffic and down pedestrian areas, e.g.:
https://i.dailymail.co.uk/i/pix/2017/09/28/10/44C62468000005...
I think the main difference in the UK is, when the situation deteriorates enough to require police with guns turn up, the guns aren't there for show to try and subdue/persuade you. They'll usually shoot to kill from what I've seen/read/heard.
I can remember going on holiday to France as a kid and being unable to take my eyes off the guns I saw on the hips of French police, because it was such an unusual sight for someone born and raised in middle England.
I think in the UK we're so used to the idea of unarmed police that we forget how astonishingly unusual it is. In most countries the idea of unarmed police is unimaginable. We've really achieved something special by managing it, at least in most parts of the country most of the time.
I wish Samsung used that fact in their marketing, I think it would really play well.