[Margaret Pilkington]

that is because the tax laws are to trap the little flies(that's you and me)...the big ones (like Lord Levy) break through.
It was ever thus...and this situation is similar to large multi-national businesses...they have highly apid lawyers to ensure that they pay little tax...so what they are doing is entirely legat.......all governments for decades have known about these loopholes....not one of them have tackled the issue...though they could have.
We don't really need to ask 'why'do we...we know the answer.