Stormystar Please get something straight. Anybody is entitled to enter the UK (or any other country) and immediately seek asylum. They are not "illegal", unless a request for asylum is refused.
There are, of course, people who don't seek asylum, so they are in the UK illegally, but I'm fed up with the sloppy use of terminology.
In 2020, the top five most common countries of nationality of people seeking asylum in the UK were Iran, Iraq, Albania, Eritrea, and Sudan. In Eritrea, for example, people are not issued with passports, so it is extremely difficult for them to apply to travel anywhere, never mind apply for citizenship elsewhere.