In October 1921, a delegation of the Dáil left by boat and train for London, where they were to negotiate with the British government for peace, unity and a republic. They came back with just one of those; and that peace didn’t last long, as war with Britain was replaced by war with their own. Were the Irish outclassed or outgunned? Were they lied to? Did they lie to their own colleagues back in Dublin? Or did they achieve the best that could be achieved, an incremental step on the way to fuller sovereignty? The Treaty tells the story of what happened inside those negotiations, as...