In order to be able to tow a caravan a driver must hold at least a Category B on your driving licence. If you passed your car test before 1 January 1997 you are generally entitled to drive a vehicle and trailer combination up to 8.25 tonnes maximum authorised mass (MAM).
If you passed your driving test after 1 January 1997 and have an ordinary category B licence, you can:
Drive a vehicle up to 3.5 tonnes or 3,500kg MAM towing a trailer of up to 750kg MAM
Tow a trailer over 750kg MAM as long as it is no more than the unladen weight of the towing vehicle (with a combined weight of up to 3,500kg in total)
More information on driving licence categories
Note: If you want to tow a trailer weighing more than 750kg, when the combined weight of the towing vehicle and trailer is more than 3,500kg, you will need to pass a further test to obtain a B+E category licensing.