P and D were drunk and P was giving D, who wasn’t wearing a seat belt, lift home, when P lost control, causing the car to crash and D was severely injured. Watkins J held that on the balance of probabilities D’s injuries would not have been lessened had he been wearing a seat belt. However where P knew the driver had drunk enough to make it likely to impair to a dangerous degree the driver's capacity to drive properly and safely OR where P had been drinking with the driver, in the knowledge that he would be given a lift home, so that by the time of driving P’s perceptions as to D’s ability to drive was impaired, P would be guilty of contributory negligence. The latter applied here. Therefore P’s damages were reduced by 20%.