you are legally required to have a piece of paper attached to the rear of the towed vehicle, with 'On Tow' scrawled on it in biro. It has to be paper in case it rains and then it will go soggy and (even more) illegible. If you can manage to mis-spell 'On Tow' so much the better.
The tow rope should be no more than three feet (approx. one metre) in length and should be no less than twenty years old. Some sort of rag must be tied somewhere along the length of the rope for absolutely no reason whatsoever.
Your journey should include at least one fifteen mile section of motorway or dual carriageway where you can drive along quite happily at 22mph with your hazard lights flashing.
This is the law. It must be, I've seen it loads of times