The King arrives in the US in the wake of more political violence – and with the special relationship in its worst state for decades. But despite the backdrop, Charles is uniquely placed to bring the two countries closer together again, writes Hugo Vickers

The state visit to the US looks fraught with difficulty - but could be key to rescuing the special relationship.

The King is facing one of the most important diplomatic challenges of his reign following a major deterioration in UK-US relations