Car licences held before 1 January 1997
All drivers who passed a car test before 1 January 1997 retain their existing entitlement to tow trailers until their licence expires. This means they are generally entitled to drive a vehicle and trailer combination up to 8.25 tonnes MAM. They also have entitlement to drive a minibus with a trailer over 750kgs MAM.

Car driving licence first obtained since 1 January 1997
Drivers who passed a car test on or after 1 January 1997 are required to pass an additional driving test in order to gain entitlement to category B+E and all larger vehicles. In addition to the new driving tests, drivers of vehicles which fall within subcategories C1, C1+E, D1 and D1+E also have to meet higher medical standards.

http://www.direct.gov.uk/Motoring/Dr...073&chk=BIZx8Z