Joe Biden accused of breaching royal protocol on walkabout with King Charles

Royal observers have criticised US President Joe Biden allegedly breaching royal protocol while visiting Windsor Castle with King Charles. 

They said the US leader walked in front of King Charles while the pair inspected the Welsh Guards.

Biden, 80, flew in his Marine One helicopter from Downing Street in central London to Windsor Castle, touching down for a ceremonial welcome from a band of red-jacketed Welsh Guards.

"The Star Spangled Banner" and "God Save the King" rang out across the manicured lawns of the stately royal residence west of London, before the pair disappeared inside.

It was Biden´s first meeting with Charles since he was officially crowned king in May. The US president did not attend the coronation but was represented by his wife, First Lady Jill Biden.

The couple had been at the state funeral of Charles´s mother, Queen Elizabeth II, in September last year, while Biden visited the late queen at Windsor after the G7 summit in 2021.

Charles, 74, is a lifelong environmentalist and Biden considers him a "clarion voice" on climate change, White House national security adviser Jake Sullivan told reporters on Sunday.

Top financiers and philanthropists are also meeting in Windsor to discuss climate finance to boost support for developing nations to cut carbon emissions.

Attending the meeting are UK energy security and net zero minister Grant Shapps and Biden´s special climate envoy John Kerry.

The UK government said more than $1 trillion is needed by 2030 to help developing economies get on track to reach net-zero carbon emissions by 2050.

Additional investment, including from the private sector, is required to cut non-CO2 emissions, halt deforestation as well as to adapt and build resilience to climate change.

Biden, who arrived in the UK on Air Force One late Sunday, is heading to the Lithuanian capital, Vilnius, for the two-day NATO meeting.