The Roman Republic was the subject of an In Our Time episode all the way back in 2004 - we listened to it last August while there weren't any new In Our Times airing. It's a pretty broad subject for a 45 minute programme - 500 years of history plus its rise and fall - so of necessity it was painting with fairly broad brushstrokes and looking at themes and commonalities across the centuries. Tackling it were Greg Woolf (St Andrews University), Catherine Steel (University of Glasgow) and Tom Holland (historian and author).
The cult of Mithras was one of several cults that sprang up in the Roman Empire during the 1st Century AD. It was a mystery cult and so what we know of it now comes from archaeological evidence and the writings of people who were not members. The experts who discussed it on In Our Time were Greg Woolf (University of St Andrews), Almut Hintze (SOAS, University of London) and John North (Institute of Classical Studies, University of London).