You have to be careful with towing on a chain ,rope or cable .
I think that since November last year ( 2013 ) towwing is now only allowed for immediate removal from danger off the carriage way unless it is on an approved set of rigid tow bars or dollies providing it is less that 750 Kg anything above that weight should have a braking system sympathetic to the tow vehicles system . Everything else is supposed to be trailered .
All towed stuff is also supposed to have a light set mimicking the tow vehicle lights and indiactors etc. , have a proper compliant number plate & correctly placed legal signage such as warning triangles and an on tow sign .
If you can only tow below a certain speed limit there is also the requirement for a flashing beacon as well .
Local to Ammanford cops do pull towed equipment ..it's an easy cop . Our builder got done around 17.00 for towing a car on a thick 3 mtrs long rope behind his van in April this year .
He also got pulled in the day time during a different week by county council officials , he got done for not being a licenced waste carrier & carrying unlicensed waste i.e. rubble even though he had a skip in his yard to put it in . ( done to stop fly tippers evidently )