Melvyn Bragg’s “In Our Time” podcasts (1,000 or so) on philosophy, history, science, the arts.
About 1 very fast hour each, hosted/moderated by Bragg with 3 guest university profs/experts. He asks questions for layman clarification along the way and inserts some personal opinions, framing and guiding the discussion which moves and jumps around fast. It is a challenge for the listener to keep up. An excellent thinking workout.