Upon reading Snell's comment about "doing some repeats" during conditioning, Lydiard said, "He doesn't know what he's talking about..." A typical Lydiards reply; and, of course, I said, "Yes, sir" (you don't want to argue the Old Man, believe me) but I don't think Arthur quite uncerstand what Snell meant either. I believe (and I'm assuming here) Peter was refering to mere "leg-speed" work. Regardless of what you might have heard from Lydiard himself, his runners sometime DID do some easy fartlek once in a while; plus all the hills they ran. Bill Baillie (and, Kim, you can confirm) used to do some 200 leg-speed even during conditioning (because he liked to race almost year round).
They liked doing repeats with equal distance recovery jog because, that way, you can maintain good speed because you'll be better-recovered; plus you can do a volume of fast work--you can do 20 of them instead of, say, 15. At that point of the program, it is important to do a volume of anaerobic running and, if you take short recoveries, you may end up finishing the workout prematurely. Some people may argue, but cutting recovery shorter, you'll be better equiped for races. Well, there are time trials at the end of the program so I guess there's no need to do that with the Lydiard program.
Running at 7-minute-pace is an interesting topic... I would argue Peter that it's not so much of 7-minute-pace but the effort. The point is to deplete glycogen in your working muscles. If the effort is too low, you'll only tap into fat-burning metabolism. So you need to do it at certain level of effort; but that effort would not be measured by minutes per mile pace. The level of speed that you run at depends on multiple factors. Once going through hill training phase, for example, you may be running the regular long run almost 1/2 minute per mile faster at the same effort because your legs are stronger and more supple, that doesn't mean you'll be running anaerobically as opposed to aerobic previously.