I recovery alot on an a-frame, saves on a 2nd driver. Both vehicles Should be taxed, Mot, If the vehicle is being towed, it should be covered by the towing vehicles insurance.
There has been alot of disscussion about A-Frames on the omegaowners forum and they also have past and present boy's in blue, normal beat to traffic, and the consensus remains a very GREY area
I have presonally towed a 3.0 V6 Omega Elite on an "A-Frame" with only a trailer board with another 3.0 Omega...100% weight 1:1 up the M5 at 56mph even passing a traffic car doing 50mph, They didn't bat an eyelid.
another occasion while filling the Fronty up with derv, while collecting another Omega NOT at 100% 1:1 A Thames Valley Traffic Car pulled along side and told me to go to the Lorry Park in the services and the Tax was out of date on the towed car. Although they let me carry on they said the Officially the car should be taxed and mot'd, or at LEAST 2 wheels off of the ground (Try That While Towing A Reliant Robin)
I agree that it depends on how the law is acted upon but also how it is interpreted