This is the reality Stu:

At present there is a Royal Navy Vanguard-Class SSBN on patrol at sea.

It is probably carrying 8 fully operational Trident missiles each armed with 5 MIRV nuclear warheads.

These missiles can be fired should the order to fire those missiles is given

If that order was given then there is nothing any outside power or agency could do to stop those missiles from reaching their targets.

Now how much more independent would you want it?