A Level Law: How to answer a problem question on negligence.

How to answer a typical 18 mark question:
Scenario
Johnny is driving his car and remembers he needs to text his mother to tell her he will not be coming home for tea that day. He manages to text his mother by holding his mobile telephone in his left hand while using his right to steer the car. As he turns the corner of the road he sees Alan coming towards him in a van. Johnny drops his mobile telephone and breaks hard but the car skids into Alan’s van severely damaging the fronts of both vehicles. Alan suffers serious head injuries.
Advise Johnny as to whether he is liable for Alan’s injuries. [18]