Complex sentence: His feat, now know as the'Bob Graham Round' was not repeated for many years (in 1960); by 2003, however, it had become a fell-runner's test-piece, and had been repeated by over 1060 people.
Split into simpler sentences: His feat, now know as the'Bob Graham Round' was not repeated for many years, until 1960. By 2003, however, it had become a fell-runner's test-piece, and had been repeated by over 1060 people.