US President Joe Biden dropped in for tea and climate change talks with King Charles III on Monday, after a garden meeting with UK Prime Minister Rishi Sunak before a NATO leaders' summit on Ukraine. 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 inspected the troops and disappeared inside.