this should answer your doubts
taken from www.dvla.gov.uk
1. 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.
Drivers who hold subcategory C1+E - limited to 8.25 tonnes MAM, may apply for provisional entitlement to the new subcategory C1+E, in order to take and pass the test which will increase their combined vehicle and trailer entitlement to 12 tonnes MAM. It is not necessary to gain subcategory C1 entitlement first but drivers have to meet higher medical standards, and pass both the category C theory test and the subcategory C1+E practical test.
LARGE GOODS VEHICLE AND PASSENGER CARRYING VEHICLE LICENCES HELD BEFORE 1 JANUARY 1997
Since 1 January 1997 all drivers who hold category C or D entitlement have been limited to trailers up to 750kgs MAM; Category C+E or D+E must be held in order to tow trailers in excess of this.
2. 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.