I think Curtis' most underrated series is The Mayfair Set. It certainly planted a seed in me regarding interest in economic history. Not to mention, "We built this city on high yield bonds".
After I posted my comment I found a huge playlist of Curtis films on Youtube, and worked my way through The Mayfair Set - very enjoyable, but I feel a bit dirty afterwards (there's a lot of shady goings on and seedy people, it feels infectious)