The answer posted by pink-kittens is the correct one.
Regulation 12 of the Motorways Traffic (England & Wales) Regulations, 1982, as amended, excludes vehicles being towed from using the outside land of the motorway.
There is nothing in the Road Traffic Acts nor in the Motor Vehicles (Construction & Use) governing the use of tow ropes.
The answer provided by voltr4m4x, besides being partly inaccurate, falls under the heading "the exception that proves the rule".
For there to be a regulation against towing in the third lane of a motorway proves that towing in the other two lanes is allowed.
Furthermore Regulation 86 of the Road Vehicles (Construction and Use) Regulations 1986 (as amended) stipulates that a vehicle (which is legally classed as a trailer when under tow) may be towed by rope or chain which must be less than 4.5 metres in length and if in excess of 1.5m the rope or chain must be made "clearly visible to any other person using the road within a reasonable distance from either side".