Ok. If you go back to those golden days of yesteryear, i.e. the early to mid 60s when Arthur was guiding all those guys to all those medals and world records, it was uncommon to find people doing long intervals, to the best of my memory. It would be great if Orville Atkins was following this and could comment, but I can't recall that many people in those days did things like mile repeats. In college in the early 70s, I think we occasionally did a 1320 (1200) interval session and might have done the odd mile at the apex of a ladder session. But overwhelmngly, we did 220s, 440s, 660s and 880s. Zatopek, Schade, Kuts, Schul? Lots of short to mid length stuff, but very little in the line of long intervals. All of which is a long way of saying that I don't believe that Arthur had his early guys doing much or anything in the line of long intervals. It just wasn't done then. The idea of intervals then was to approach or exceed race pace and that was much more likely to happen if you were doing 220s or 440s than miles. The sort of benefit you'd get from long intervals was the sort of thing that Arthur got for you with steady, up tempo runs.
But if you look at later books, you see that he does assign sessions like 3x1500 or 3xmile. Now, in those e-mails with Antonio, he sort of showed a preference for doing that sort of work (the Lydiard up tempo run) by doing longer intervals. He probably has his reasons for that. We sort of agreed that you could do it either way and he liked to put the success of Portugese runners up as evidence for his preference. Personally, I've always thought that coaches like to have athletes do intervals whenever possible because they can observe and control an interval session whereas sending guys out for a run through the roads or trails requires some trust that the athletes will do what they're supposed to and do it right. Maybe the reason Arthur didn't share this preference was because he actually ran with his athletes and could see what they were doing on those steady runs.