In the gadfly historian’s classic The Struggle for Mastery in Europe, diplomacy is less a stately art than a dangerous game of miscalculation and bluff. Seventy years on, the world it describes still feels disconcertingly familiar. “We seek nothing but the security which comes from the balance of power.” The words were attributed by Lord Acton to William III in Acton’s lecture on the War of the Spanish Succession (1701-1714), as one of the English king’s last conversations sp