When I returned the car the inspection guy decided to check the underside of the car despite the fact that it was not checked for anything when I collected it and that it is not possible to mark any damages of the underside on the report you sign when you leave. The guy very quickly found a small scratch on 5 inches - a scratch you would need to go under the car with a light to see. My guess is that they knew it was there already. That costed me 300 GBP. The company afterwards confirmed in writing that they expect the customer to control the underside of the car carefully themselves even though they are not encouraged to do so by the staff when they hand over the vehicle.