David Cameron greets foreign minister with unusual hello in front of the Queen

The Prime Minsiter was spotted tapping Hugo Swire

David Cameron speak with Hugo Swire

David Cameron greeted his Foreign Minister in a less formal manner than might be expected from a prime minister at a state banquet to welcome the Chinese President Xi Jinping.

An excitable Mr Cameron was spotted trying to get Hugo Swire's attention by tapping him on what appeared to be his behind. But Mr Swire didn't apear to notice and only turned around when the PM leaned in and spoke to him.

Unfortunately for the Prime Minister, his relaxed moment was spotted by ITV’s deputy political editor Chris Ship, who did what any self-respecting journalist would do and shared a video of the greeting on Twitter.

Jeremy Corbyn was also spotted at the event, suited and booted in formal dinner dress and a white tie. The Labour leader's outift came in stark contrast to his usual no tie, top button undone sartorial standard that has sparked such fierce debate.

Mr Cameron will host talks with Xi Jinping at Downing Street on Wednesday in a bid to seal a trade deal worth millions before the end of his four day visit.