On the 26 July London demonstration against Israel's assault on Gaza, I confronted a man who was carrying a placard which read “Research: The Protocols of the Learned Elders of Zion”, with an image of a Star of David, dripping blood, with “666” in the centre. The Protocols are an anti-Semitic forgery dating from Tsarist Russia, which purport to expose a Jewish conspiracy to dominate the world. They were used in their time, and have been used since, to whip up racist hatred, often violent, against Jews.