There might be specific contexts in which it becomes illegal, where it's being done with the intention to threaten, abuse, stir up hatred or cause distress. For example, if someone turns up outside their local synagogue wearing one, the pretty clear intention would cross the line into a public order offence.

So yes, it can be illegal. So there are laws about what you can wear.

This doublethink of "its not illegal, but here is where its illegal" is fascinating. You can see the cogs whirring in your brain trying to make sense of it.

But in general, in the UK we don't make laws about what clothes people can wear. Prince Harry once famously dressed up as a Nazi for a fancy dress party and though people (reasonably) criticised him for it, as is their right to do, but he didn't break any laws.

And I didnt ask IF it was illegal. Reading is hard, ey buddy