Quietly? No, twist up sharia law and give them the blade.
Since it is a capital offense to leave the islamic faith - Saudi Arabia is busy killing people for this very reason right now - it ought to be a similar crime to leave a pure islamic nation. Unless it’s to wage jihad.
So, if they give it up and leave the IS Caliphate and return to UK, give them the chop. Lengthwise*. For either apostacy from the pisslamic standpoint, or nascent terrorism from the British standpoint. Either way, you win and they lose. A small bit of legal wrangling would extend this punishment to those who attend pro-sharia demonstrations in UK, even if they’ve never left England before. Obviously they are split, culturally.
* this is only fair, since they are, as Kim DuToit once pointed out in a different situation, “soutpiel”; they have one leg in the west and one leg in the islamic world. With their wieners dangling in the salty ocean. Hence the origin of the phrase. They’re culturally split, so let them be physically split as well.
Isn’t appeasement of the Nazi’s what lead to WWII?
I just find it so sad that anyone can let this barbaric bunch of murdering scum be called anything other than barbaric murdering scum. And a danger to the civilized world.
Sad that my children and grandchildren will have to be cleaning up this mess. For a long time.