There were 14 American presidents in power during the Queen's 70-year reign - and she met them all except one.
Lyndon B Johnson, who took office in 1963 following John F Kennedy's assassination, never crossed paths with the Queen during his just over five years in power.
The monarch played a pivotal role over the decades in the UK's relationship with the leaders of one of its closest allies. She went riding with Ronald Reagan, developed a warm friendship with the Obamas and shared "automatic chemistry" with Donald Trump, according to Trump himself.