Bearing in mind that travel restrictions do little or nothing to prevent the spread of infectious diseases, I wonder why the government has done that?
It's my guess that they've done it for the same reason as Mr Johnson appeared on the telly on 20th March 2020, announcing grimly "You must stay at home." He did this, not as part of the UK's well rehearsed and WHO-approved plan for coping with a pandemic, which involved no lockdowns, no masks and no travel restrictions. He did it because Italy panicked, locked their country down and the rest followed like dominos.
There followed one of the most disturbing periods in this country's history, with two years of often bewildering and complex regulations which assaulted personal liberties, enforced by criminal sanctions. Among these (among many others) was one which compelled diners to wear a flimsy, ineffective mask whilst walking through a restaurant to go to the toilet (though not for the two hours they spent eating their dinner) and the question whether a Scotch Egg was a "substantial meal" almost ended up in a court of law.
So be afraid, folks, be very afraid. They've done it to you once (when they never thought they'd get away with it). They'll do it again if they think you won't kick up a fuss.
There is no reason on Earth why restrictions should be placed on visitors from China. A quarter of a million have already arrived this year, with either student or family visas. A lot more have almost certainly arrived for other reasons. "Ordinary" 'flu is a far greater threat to health and the NHS than Covid is. There are very large numbers of cases and hospital admissions at the moment. So stand by for the Twittersphere to get to work, imploring the government to "do something" to combat the problem. Restrictions on visitors from China will be the kindling they need to get another campaign going to "Save lives and protect the NHS."