Did you know that drivers who passed a car test on or after 1 January 1997 are required to pass an additional driving test in order to tow large trailers and gain entitlement to category B+E. Category B Vehicles up to 3.5 tonnes MAM and with up to 8 passenger seats may be coupled with a trailer up to 750kgs MAM (allowing a combined weight up to 4.25 tonnes MAM) OR a trailer over 750kgs MAM provided the MAM of the trailer does not exceed the unladen weight of the towing vehicle, and the combination does not exceed 3.5 tonnes MAM.

https://www.2nd2nonedrivingschool.co.uk/car-and-trailer-testing-b-e.html