When members of the Royal family saluted as the late Queen’s coffin was carried into the Abbey, he gazed straight ahead.
In the front of the south transept of Westminster Abbey were Realms governors general and then Commonwealth countries followed by other nations.
While Mr Biden arrived in his armoured car, nicknamed The Beast, others were spotted catching the bus.
Coach services laid on by the authorities departed from outside Royal Hospital Chelsea, where a line of police had closed off the road to welcome visiting dignitaries.
World leaders were seen being ferried to the funeral by transport firm Westway, which operates Britain’s “first and only” zero-emission coaches.
The firm, which is based near Hampton Court and holds a Royal Warrant, runs a fleet of electric buses which use solely battery power.
A steady flow of the coaches was spotted heading to Westminster Abbey. They have 4G Wi-Fi and carry between 49 and 51 people, according to the company.
Jacinda Ardern, the prime minister of New Zealand, shrugged off suggestions that some dignitaries would be unhappy with the arrangements.
“I don’t think the bus warrants too much fuss,” she told the BBC. “It just makes good sense. We’re a very practical people.”