Driving without a driving licence – trailer to driving licence KL. b

Hello, what kind of punishment does one expect if he drives a car with trailer, which may pull the trailer according to the vehicle registration, but the driver owns only a driving licence of class B? Background, an acquaintance drives an off-road car and absolutely had to transport something with the trailer. In addition, he makes the ride. When turning someone drives him in, he does not blame himself, the accident opponent did not look up and had worn-out tires. What kind of punishment can Wait for my friend?