Complex sentence: It was first run in 1920 at a distance of 2,400 metres, which was increased to 2,600 metres in 1963, and to 2,700 metres in 1973.
Split into simpler sentences: It was first run in 1920 at a distance of 2,400 metres. This was increased to 2,600 metres in 1963, and to 2,700 metres in 1973.