The PhD Comics creator was detained in the UK for being a cartoonist?

So he earns a living as a cartoonist. Because of that he's invited to give talks. He gets money for these talks. How is this not working?

I can just imagine doing the same in the USA. Not.

Not so long ago when my wife (British) and I (Australian) went to Melbourne she was invited to give a lecture related to her work. The advice we were given was - accept no money at all, even for expenses.

If he didn't bother to check on these things then I have very little sympathy. The other countries almost certainly have similar conditions, and mostly things are fine if you check in advance.

If he's receiving payment for those lectures, he may need a work visa. They're pretty strict about that stuff at the border.

Maybe they were afraid he would draw a cartoon of Muhammad and cause an international incident. No, on second thought the work visa theory makes more sense.