If it's designated by the landowner as vermin there should be no legal reason I can see why they can't be shot now.

Anyone thinking the UK Govt is farsighted enough to control these through hunting is away with the birds. That's logic for goodness sake, when did a modern Govt use that? Whatever gets the most votes is what dictates Govt policy and hunting 'aint it.

They'll either ignore it until it gets out of control and then wring their hands or they will most probably leave the control of them to licensed Vermin control companies. ( Unless of course they start spreading disease in which case it will be like the Foot and Mouth outbreak where they have the army driving around shooting them with 5.56mm FMJs and wondering why they don't fall over ).