There was a hill phase. He changed things over the years though. And of course he stopped coaching athletes directly and coached coaches like with Athletics Finland and in about five other countries.
So at first the hill phase was four to six weeks with a lot of hill bounding, hill circuits and various drills etc. I believe and I may be a little off here, but he designed the hill phase more for middle-distance runners than say marathoners or 10,000 et al. The purpose was to build explosive power in the lower leg area, feet and ankles, so that the runner can take their aerobic development and general muscular and nuero-muscular coordination and really take advantage of it with a complete package, leading into the anaerobic phase, which most people incorrectly call "speed work".
There is a lot of power that can be developed in the ankle, foot and lower leg that many athletes neglect and it is/was especially true during the big comfy/controlling shoe hysteria that went on: "protecting" the feet: weak feet at the end of very powerful legs = less execution of the whole mechanical aspect and worse, injuries.
He scaled back the hill phase as it was very daunting.
Now I know someone will come on here and say, "if there was a change, then it wasn't "Lydiard"". Which of course is dumb. The principle was to develop the lower leg, foot, ankle area like a ballet dancer - if you watch a ballet dancer and try that action out, you will then realise the incredible power that can be developed.
Purpose: Power development in the lower extremeties, hidden speed/anaerobic work and form work. Some quad development and development of the lifting muscles. Total muscular coordination. Turnover and stride lengthening exercise on the downhill portion of the hill circuits.
Now saying this, there are sworn "Lydiard coaches" who don't use a hill phase. I have interviewed a few world-class coaches who have coached gold medallists who didn't use a specific hill phase.
Rod Dixon is an example of a guy who grew up in a hilly area, Nelson, New Zealand. Did he atrophy when he moved away? I don't think so, he ran a ton of hills regardless. Did he need a specific hill phase? Probably not as much as a flatlander. So what is good for John Davies or Barry Magee or Lasse Viren, may not have been appropriate for Lorraine Moller or Dick Quax etc etc.
We can't just look at a Lydiard schedule and say,....TIME FOR HILLS NOW FOR FIVE WEEKS! Because that is the time to do it....the method is based on a set of principles and yes a timeline that is well documented out there, something to the effect:
Aerobic Development (as long as necessary: 8 weeks to however long it takes to create the desired effect)
Hill phase 4 to 6 weeks (continue mileage levels)
Anaerobic phase 4 to 6 weeks (new can of worms, right here)
Coordination phase 2 to 4 weeks.
Taper if and where and when necessary 2 weeks
Race.
Continuation.
I am a lousy runner, but within my own paradigm really saw a big change when I realised what I needed was a tonne of regular hilly running and the classic Lydiard 2 x 90:00 (Tues/Thurs) and 1 x 3:00:00-plus added to my running....worked! That was what I needed. Next guy might require different stimuli. The art is to recognise it.