A frames are legal but only if the car you are towing is legal, ie taxed and tested. Again though you need to have the correct entitlement on your licence. What alot of people don't seem to realise is that its all to do with weight too. So to put it in easy terms you cant carry a cossy saph on a b/ James double axle trailer if youre towing it with a smaller car, say an escort. This is due to a weight imbalance, they are very strict on towing these days