I see this is the second episode in the series, and I missed the first one, but tonight's documentary on SBS "Battle Castle - Chateau Gaillard" was very good.
I did point out to my son that I somehow doubted that Richard the Lionheart and King Philip of France really had their strategy meetings while fully suited up in chainmail, as the re-enactments indicated.
Still, it taught us quite a bit about castle design, and then castle siege techniques, of 1200.
The show is available on SBS for another 2 weeks. Beyond that, I can't see it on Youtube, but the Wikipedia entry on the castle is pretty detailed.