The idea is to one day spend a long time on your feet (the only way you can do that is to go slow enough so you won't die prematurely); followed by the next day to work a bit harder on your breathing (call it tempo, threshold, AT whatever) but shorter in duration.
That would be a whole package but you need to be strong enough to handle that kind of regime. Lydiard realized that and later started to say "nucleus of marathon conditioning being three long runs a week (whatever long means to you)". When building up mileage, most people can't handle the level of effort Arthur's Boys did simply because most people don't have the background they had. When they try to build up the long runs, even for Peter Snell at some point, in-between "shorter" runs becomes mere recovery runs from the long runs. That's fine too initially.
When constructing the Lydiard regime, think about what you need to focus on developing at each phase. During conditioning phase, the main emphasis should be to build aerobic base. The best way to do so, according to Lydiard, is to go for long runs; preferably anywhere between 90 minutes to 2 hours. Initially, forget the efflrt; becasue, as you get fitter and stronger, the pace will quicken. Some people might be concerned with "mechanics" during this phase. If so, throw some hilly courses; do some easy strides one a week; have a fartlek workout one day... It's okay to do long reps at moderate effort in place for "3/4 effort 10 miles" in the original schedule--I used to do that because I couldn't push myself to do a kind of tempo the schedule calls for; so I broke it down in segments. But those are NOT the main focus. Main focus here is long runs. If, for exapmle, you absolutely have to skip a day or two during the week (for whatever the reason), don't skip the long runs. We call them "key workouts" or "point workouts".
Effort is of importance. But if you can't handle doing high end effort short runs the day after long runs, make them just a recovery run but throw some effort into those long runs. Ron Daws used to have what he called "aerobic fartlek" and threw marathon-race-pace sections during his longest runs. I guess you can classify what Squires used to do in the same category...
Full-scaled Lydiard program is very difficult for anybody to handle. Most people, if tried, come out discouraged or disappointed or disgusted! Understand the principles of the program and apply it to your own needs. If Snell and Magee did Monday 10-miler in 55 minutes, that doesn't mean you need to do a 10-miler on Monday at 5:30 pace to be successful.