Joe Biden receives royal salute as he greets Charles at Windsor Castle

Joe Biden risked breaking royal protocol today as he walked two steps in front of King Charles at their meeting at Windsor Castle.  

The US President, 80, arrived to talk with the King about climate change after earlier sitting down with Prime Minister Rishi Sunak in the Downing Street garden. 

As the pair inspected a guard of honour formed by the Welsh Guards, Mr Biden walked two steps ahead of the King. 

Charles did not appear to take issue with the apparent faux pas, as both men laughed and smiled while talking and the President was treated to a rendition of the US national anthem. 

Etiquette expert William Hanson told MailOnline it is ‘more standard practice’ for heads of state to walk alongside each other, and put down the slip-up to Mr Biden possibly being so relaxed in the King’s company.

Donald Trump, Mr Biden’s predecessor as President, sparked criticism in 2018 when he walked in front of the late Queen Elizabeth II during a visit to Windsor. 

Mr Hanson said: ‘It is more standard practice for both heads of state to be alongside each other. 

‘That is certainly what we have seen in any country when this is being practised.’

Asked why he might have walked in front of the King, Mr Hanson said: ‘He was either so relaxed or just got carried away. Sometimes it is they don’t listen to their briefing. 

‘Sometimes they are nervous too. Windsor is an intimidating environment.’

Mr Biden was also pictured with his hand on the King’s back. 

Mr Hanson said: ‘It is not generally the done thing to touch royalty. 

‘However Biden is a head of state, the protocol among heads of state is they are amongst equals. 

‘If that had been Queen Elizabeth, there would be more outrage. What we are seeing with Charles’s reign is that it is much more informal than his mothers. ‘

‘And so what was an absolute no no under her, we are now seeing a more contemporary and tactile monarchy. 

‘The whole point of this is to show friendlienss, this perhaps is a good example of where protocol is changing where the times change. 

‘They are men of similar ages and have got a lot in common, and the King is very easy to chat to.’  

The President’s meeting with the King today came after a phone conversation earlier this year that Biden’s national security adviser, Jake Sullivan, described as ‘incredibly warm’.

Earlier, in his meeting with Mr Sunak, the President  told reporters relations were ‘rock solid’ – as he tries to quash his ‘anti-British’ reputation. 

Mr Biden last had formal talks with Charles at the COP26 climate summit in Glasgow in November 2021. 

He attended the state funeral of Charles’s mother, Queen Elizabeth II, in September, but did not go to the Coronation – with his wife, Jill, attending instead. 

Mr Sullivan said the President has ‘huge respect’ for the King’s commitment on the climate issue in particular.

He said Charles has been a ‘clarion voice’ on climate and ‘someone who’s mobilised action and effort.’

‘So the president comes at this with enormous goodwill,’ Sullivan told reporters yesterday as Biden flew to London.

Before making his way to Windsor Castle, Biden sat down for a friendly meeting with Mr Sunak at Number 10. 

However, frustration is mounting that although it will be their fifth meeting in as many months, Mr Biden is largely ignoring the UK’s views.

More flashpoints have emerged over recent days, with Mr Biden pouring cold water on the idea of Ukraine joining Nato anytime soon.

He has also put Mr Sunak in an awkward position by declaring the US will supply Kyiv with cluster bombs – weapons the UK is committed to shunning.

And the pair could have tricky exchanges over the next head of Nato, after Mr Biden seemingly blocked the ambitions of Defence Secretary Ben Wallace and backed the EU’s Ursula von der Leyen for the top job.

Tory MP David Jones told MailOnline engagement was useless if there was no ‘positive response’. 

‘The PM should remind him which country is America’s strongest ally,’ he added.

As the leaders sat down on rattan furniture in the Downing Street garden, Mr Biden told Mr Sunak he ‘couldn’t be meeting with a closer friend and greater ally’.

‘Our relationship is rock solid,’ he said.

Mr Sunak said the pair would consider ‘how do we strengthen our co-operation, joint economic security to the benefit of our citizens’.

He added: ‘We stand as two of the firmest allies in that alliance and I know we’ll want to do everything we can to strengthen Euro-Atlantic security.’

Mr Biden is said to be pushing for the current European Commission president to take charge of the military alliance.

But MPs complained that he is ‘being a d***’, after apparently being angered by Britain failing to get his approval to train Ukrainian pilots for F-16 fighter jets.

Conservatives have warned that Ms von der Leyen was the ‘worst ever’ German defence minister before becoming commission president. 

On her watch Berlin’s troops notoriously trained with broomsticks on Nato exercises because they did not have enough rifles.

Mr Biden told CNN in an interview broadcast as he set off on his journey that Ukraine was not ‘ready for membership’ in NATO.

‘I don’t think there is unanimity in NATO about whether or not to bring Ukraine into the NATO family now, at this moment, in the middle of a war,’ he said.

He noted that NATO members are committed every inch of each other’s territory, while war is raging inside Ukraine.

‘If the war is going on, then we’re all in war,’ he said.

His tone appeared far more downbeat than the UK, which has urged a positive message on the prospects for Ukraine joining Nato.