I remember watching some interviews with him on Youtube where he talks about training. From what I recall, he runs mostly doubles during the week, a low key race (e.g. Parkrun) on weekends, plus a long run. He runs mostly by feel. He said something about not having a coach because he would never listen to the coach.
I also found this snippet in the Runners World article linked below from a few years ago:
His training hasn’t changed much over the years. When he’s building up for a marathon, he’ll run 120 miles a week; when he’s not, he’ll drop down to 60. His daily staple is 10 miles in the morning and 10 in the evening. On Sundays he’ll do a long run of 17 to 21 miles, and once a week, he’ll join in a track session with his club, Termoneeny Running. He doesn’t monitor his heart rate or his times, instead running by feel.
