Complex sentence: London Championships 1969/70, held at Islington Green Secondary School (December 29,1969-January 3,1970) and less than a year later, at just fifteen years of age, he proceeded to Oriel College, Oxford, to study mathematics.
Split into simpler sentences: London Championships 1969/70, held at Islington Green Secondary School (December 29,1969-January 3,1970). In 1970, at just fifteen years of age, he proceeded to Oriel College, Oxford, to study mathematics.