PM: I'm here in Runnymede on the banks of the Thames. It's the 15th June and 800 years ago on this spot, King John sealed the Magna Carta, the great charter, under pressure from barons to stop so much arbitrary rule. That document set out for the first time, so many things that we take for granted: freedom from arbitrary arrest, the rule of law, the idea that there were limits on executive power. It's not just important in British history, but actually it's important for the rest of the world. I