Assuming that the caravan has a MAM (Maximum Authorised Mass) of over 750kg, which most will, you will need a B+E license as stated above.
EDIT: Scrap that, it looks like “You can also tow heavier trailers if the total weight of vehicle and trailer isn’t more than 3,500kg.”
https://www.gov.uk/driving-licence-categories
EDIT 2: “A caravan over 750kg MAM as long as the combined weight of the car and caravan is less than 3500kg Gross Train Weight (GTW) and the MAM of the caravan is less than the unladen weight of the car.” So not only does the whole shebang have to weigh less than 3,500kg but also the MAM (Maximum Authorised Mass) of the trailer has to be less than the unladen weight of the car.