It's funny what "we" would do in Court.
The offence is "Absolute" and no intent has to be proved. The only factor involved is that can the gun shoot over the stated limit.
The only argument we can use is that the test was incorrect/gave the wrong results.
This is impossible to do as there is no standard test. It doesn't matter what other guns would do as it's you and your gun that is in Court.
Saying that your gun is no different to all the others out there may well be a valid point but yours shot over power.
If we're saying that all guns are illegal, then perhaps we're correct according to the legislation. A more important point that could be argued is that as a Subject of this Country you are being prevented by a third party from complying with it's legislation. Bet there's miles in that one and plenty of money for the "Civil Right's" Lawyers.
Someone please tell me of another instance where you are prevented from complying with the law. It may well be that in this case the fitting of AT is actually illegal.