If you passed your standard car test after 1st Jan 1997 the law changed regarding towing.
Since then you are only allowed to tow a trailer with a combined weight (car and trailer) of up to 3,500kg.
Before then you were allowed to tow a trailer with a combined weight (car and trailer) of up to 8,250kg.
You are allowed to tow an unbraked trailer weighing up to 750kg with a car weighing up to 3500kg (total 4250kg) but for our purposes we won’t be covering this as caravans weigh more than 750kg.
There used to be a law which said you couldn’t tow a caravan weighing more than 100% of the car’s kerbweight, but this was removed in 2013. You can legally tow up to the car’s towing limit as long as you stay within the 3500kg limit.
These weights are based on the MAM (Maximum Allowable Mass) figures for the car and caravan, in other words, the maximum laden weight, whether they are loaded to that level or not.
For example: if you were to tow a 1500kg MTPLM caravan with a car with Kerbweight of 1500kg but GVW 2010kg even if the car and caravan were unladen, you would be breaking the law (as the total would be 3510kg). If you hitched up a trailer capable of carrying a car, even though no car was on it, you would be breaking the law.
Please bear in mind it does not matter if the car transporter trailer is empty (no car on it), it is the allowable weight on the trailer weight plate that is important, so even though the trailer may weigh only 1,000kg unladen, it would still be illegal to tow as it’s laden weight would be too high to fit within your limit.
If you are unsure what your Driving Licence category means here is the relevant checklist https://www.gov.uk/old-driving-licence-categories