The State Opening of Parliament. The most magnificent royal occasion of the year. The Queen, her Cabinet and all the most powerful people in the land are gathering in one room, the House of Lords. And none of them know they are about to endure the most terrifying day of their lives. Not all of them will survive.

Sitting amongst the hostages are two young men, the sons of the British Prime Minister and the US President. It creates the cruellest challenge any leader could face. As the world watches on live television and holds its breath, President and Prime Minister are torn in two between their duty as statesmen, and their love as parents.

Yet others have their agendas, too, not least of them Harry Jones, a man who is already undergoing the worst day of his life when he becomes swept up in the maelstrom. What can he do about this act of terrorism when the most powerful people are rendered helpless? He can ask one simple question - why?