Note the important thing, his CONSISTENCY.
Ron Clarke training from "The Lore of Running" Noakes 1991:
"Clarke's training methods have been described by (Fred) Wilt (1972), who reports that Clarke trained almost daily year round with little variation from one season to another. Any variation was unintentional. Each days workout was remarkably similar and he did not attempt to peak. Rather he remained racing fit year round gradually increasing the quality of training over his athletic lifetime.He seldom trained on the track, did not keep a training diary, and never used a stopwatch during training. Most of his training was done on grass and roads and much of it was done over extremely hilly courses.
Clarke trained three times a day, but regarded the evening workout as the truly important part of each days training. On weekday mornings he ran 5k continuously at a fast pace and thereafter did some gym work. From 1:00 to 1:45 he ran 10-12k at a fast pace and in the evening he ran 16-25k also at a fast pace. He usually did this workout while wearing a full track suit unless the weather was extremely hot. On Tue. & Thu. he included gym training. On Sat he ran only once 16-25k and on Sun. one run 28-34k fast pace over rolling hills.
Occasionally but not more than twice a week he would run ten 200m or 400m intervals with equivalent recovery jogs between repetitions. On runs 16k to 24k pace 3:08/k for the distance. He ran hard and forced the pace almost without exception on most of his training runs.
http://www.letsrun.com/forum/flat_read.php?thread=154189