Melvyn Bragg would always rush the experts, pressuring them to get to the point asap. I found him a bit off-putting and even rude at times, but it was what made made the show unique and never stagnant.
That's the only way they managed to cover such big subjects in relative depth in such a short slot! All the guests are used to waffling for a full uninterrupted hour to captive audiences about tiny segments of each topic; without that pressure the show couldn't exist.