The United States and the United Kingdom have long enjoyed what Winston Churchill dubbed a "special relationship" - yet no US president has ever attended a royal coronation. Does this tradition point to an underlying antagonism between the two nations - or something more mundane?

The Coronation of King Charles will be marked by centuries of pageantry and tradition. The King will swear his oath in Westminster Abbey in front of thousands of his subjects and heads of state.

But there will be one glaring absence among the throng of dignitaries: US President Joe Biden.

He was invited, the White House told the BBC.

But in a phone call with the King, the president said he would send his wife, First Lady Jill Biden, and a diplomatic envoy, instead.

The White House gave no reason for Mr Biden's absence, but said the President had "conveyed his desire to meet with the King in the United Kingdom at a future date".

The no-show has sent ripples across the pond.

Conservative MP Bob Seely told the Telegraph that Mr Biden seems "pretty remiss" to skip the "once-in-a-lifetime event".

Russell Myers, royal editor at the Mirror newspaper, also told Sky News that the president's absence was due to his being "staunchly proud of his Irish roots, his Irish American roots".

"I didn't think it was a real possibility that he would come," Mr Myers said.

But historians say the reason is far less political, and that it's actually a centuries-long tradition for American presidents to miss the coronation.

'It's not a snub'
"I certainly don't view it as a snub on President Biden's part," said Laura Beers, a professor of history at American University, who specialises in modern Britain.

"It is a non-story in terms of the idea that Biden is anti-British," she said. "He's not going because no American president has ever gone to a coronation, so why start in the 21st century."

Before the reign of Queen Victoria, Ms Beers noted that the US-UK relationship was largely adversarial, following the American Revolution and the War of 1812.

Queen Victoria's accession to the throne ushered in "Victoria Fever" and a new era of American fascination with the British monarchy, but even then President Martin Van Buren did not attend the ceremony.

"It was not practical for an American president to come, and I think it just became tradition after that," Ms Beers said.

Troy Bickham, a fellow with the Royal Historical Society and a historian, said travelling overseas wasn't practical before transatlantic air travel began in 1939, three years after the coronation of King George VI.

Eisenhower and Elizabeth
The Second World War marked a turning point in the diplomatic relationship between the United States and the United Kingdom, according to historians.

Throughout the war, King George VI and his daughter, then-Princess Elizabeth, developed a relationship with Dwight D Eisenhower, who served in London as the Supreme Commander of Allied Forces and supervised "Operation Overlord," the D-Day invasion of Normandy.

Mr Eisenhower was elected 34th President of the United States just months after King George VI died and Queen Elizabeth II ascended to the throne.

But despite his close ties to the UK, Mr Eisenhower chose to keep to tradition and send an envoy to the coronation instead.

Historian Sam Edwards noted that the US was embroiled in the Korean War at the time, and President Eisenhower would also have been needed in
President Eisenhower's absence at the coronation didn't hinder his relationship with the UK or the royal family.

In October 1957, the US welcomed Queen Elizabeth II for her first official state visit as monarch. Two years later, the Queen hosted President Eisenhower and his family for a less formal visit at her royal estate in Balmoral.
One queen, 14 presidents
As Britain's longest reigning monarch, Queen Elizabeth II ruled through 14 US presidencies, and met all but one president during their tenure in office.

Three sitting US presidents have made official state visits to the UK, while the Queen made four state visits to the US during her reign.

While he appears to have chosen not to break with tradition by sending an envoy in his stead to the coronation, President Biden has already accepted an invitation from King Charles for a state visit. A date has not been set.

No matter who attends the coronation, Mr Edwards said King Charles presides over a renewed commitment to the diplomatic relationship between the two countries.

Attending the coronation, he said, "is but one piece of the contemporary transatlantic relationship puzzle." (BBC)

Update news