Taxi!
I'm not sure if this'll be of any help regarding the legality of towing:
The following is an article printed in the Feb issue of Freewheel - the magazine for the Rover Sports Register:
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Towing on "A" frames
A comment in a club journal to the effect that a member had had a brush with the law as a result of being in the habit of towing his rally car to and from events on an A-frame has prompted this note, which relates only to towing by cars and light commerical vehicles. Different rules apply for agricultural vehicles, motor tractors and road locomotives.
Regulations 19 and 22 of the Road Vehicles (Construction and Use)Regulations 1986 (as amended) make special provisions for the recovery of vehcilesthat have broken own during the course of a journey - they may be recovered using appropriate equipment, including a-frames. The Road Traffic Act imposes a speedl imit of 20mph on ordinary roads and 40 mph on motorways for vehciles being recovered in this way, and that applies to broken down ehciles being towed by rope, solid bar, dolly or A-frame.
other than such breakdown recovery situations, the C & U regulations treat vehciles connected by a rigid coupling as towing vehicle and trailer. The use of an A-frame thus means the towed car becomes a trailer in the eyes of the law, and must therefore comply with the normal requirements of a trailer.
The same C & U regulations require trailers over 750kg gross mass to have brakes that are either operated directly from the towing vehicle or that operte on the overrun. Unbraked trailers may not exceed 50% of the gross mass of the towing vehicle. A device that applies the brakes on the trailer if for any reason it should become detatched is required on trailers above 1500kg gross, but below that limit secondary couplings (such as chains) may be used.
A-frames can really thus only be used legally for towing cars if a) that car is being recovered after a breakdown b) the gorss weight of the towed car and A-frame is below 750kg or c) there is some fail safe mechanism to apply the brakes of the towed car. The lights on the rear of the towed vehicle ave also to comply with the C & U regs for trailers, including warning reflective triangles and towin vehicle registration plate.
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My own thought is that if the towed car is a trailer then it doesn't need tax, mot or insurance..