I have to repeat myself that most Muslims are not Islamists any more than most Christians are walking the path of Jesus.
If you are on the far right or the far left, you have gone too far.
I can believe they allow Islamists to become British citizens as no honest Islamist could ever take the Official Oath which is a promise to be loyal to the British monarch, and their heirs and successors, sworn by newly naturalized subjects in citizenship ceremonies.
“I, [Insert full name], do swear that I will be faithful and bear true allegiance to His Majesty King Charles, his heirs and successors, according to law. So help me God (Allah).”