Class C licence

J-BONE:
If a driver has a full class C licence can he drive an 18.000 gross / 21.500 GTW lorry if he is towing a 2.5 ton braked trailer?

or
can he only tow a 750kg trailer braked or not?

Only a 750kg plated MAM trailer

gov.uk/driving-licence-categories

Large vehicles
Category C
You can drive vehicles over 3,500kg (with a trailer up to 750kg MAM).