The following information has been provided by
PCT Automotive who are one of Europe's leading designers, manufacturers and distributors of towbars, towing equipment and automotive products, PCT Automotive also operate one of the largest towbar fitting operations in the UK, for more details visit their website
Any light passenger vehicle registered in the UK on or after August 1st 1998 ('S' Registration) will require a type approved towbar and towball (when fitted).
Light Commercial Vehicles and Car Derived Vans are not covered by Type Approval. (LCVs continue to be exempt and are unlikely to be covered for the next 5 years or so).
This legislation will not be retrospective, therefore any vehicle registered before August 1st 1998 will never require a type approved towbar (e.g. 'R' registered vehicles will never require type approved towbars).
Any vehicle requiring an approved towbar also requires an appropriately approved towball. Towball 'D' and 'S' values must match or exceed the towbar 'D' and 'S' values.
Type Approved towbars and towballs can be identified by the presence of a Type Approval label which must be visible even when the product is fitted to the vehicle. This label will have as a very minimum, the product code, a 'D' value, an 'S' value and a European approval number in the form e11 00-01234. These labels must not be removed or defaced as this will invalidate the towbar manufacturer's warranty and would result in the towbar or towball not being identified as Type Approved.
The above text is the 'Translation' for the full information on Type Approval EC/94/20 including the legal definition visit PCT Automotive's website and click on the Law button
Also: Drop plates must never be used to raise the height of the towball, this is dangerous and illegal. They can also NOT be used legally to lower the ball on a post 1998 vehicle unless the towbar has been type tested with it fitted.