A school pupil has made history by becoming the most decorated competitor in the International Mathematical Olympiad's existence.Alex Chui, a Year 13 pupil at Tonbridge School in Kent, achieved a flawless score of 42 out of 42 at this year's contest in Shanghai, finishing joint first and claiming his fifth gold medal.With five golds and two silvers to his name, Alex now holds the all-time record for the most successful individual performance at …