Does your son have "commuting" on his insurance? If he does not, he is technically guilty. If he does, then attend court and show the judge. I have heard of this situation before and the police are wrong. As long as there is a policy in place, the insurer has to provide cover under the road traffic act to any third party claimant.Ie Your son IS insured. It would then be a matter between your son's insurer and him, not the police.

The other point is, just because your son was going to work, does not mean he was necessarily going there TO work. The legal question is, was there the provision of a legal insurance policy at the point your son was stopped? Also, was the vehicle seized? Or did they allow your son to continue? If so, that weakens their case, as they have now knowingly allowed for an uninsured vehicle to be on the road. Do some research on Mckenzie friends who assist people at court. See also see Citizens Advice to see if they can assist in attending court.