Resurfaced Letter Reveals Prince Philip 'Woke Up in a Cold Sweat' After He Visited the Nixon White House

Even royals aren't immune to the nerves that come with meeting a U.S. president.

A newly resurfaced letter sent by Prince Philip to Richard Nixon in 1969 reveals the Duke of Edinburgh "woke up in a cold sweat" for fear he had not delivered an adequate toast to the president after a visit to the White House.

The letter, recently dug up by the archives team at the Nixon Presidential Library, gives a glimpse at the personal interactions between royals and American politicians — and sheds light on the diplomatic charms of the late prince, who died Friday at the age of 99.

Watch: What happens to The Duke of Edinburgh title now?

The correspondence was written after Philip visited the White House solo, without Queen Elizabeth, for a dinner hosted in his honor.

Though the evening seemingly went well, Philip wrote that he woke up "in a cold sweat" after realizing he had forgotten to make a toast to President Nixon's health, adding that his contribution to the remarks delivered by others was "very lame."

"Dear Mr. President," his letter reads. "I can't begin to tell you how much I appreciated your very great kindness and hospitality at the White House. I was quite overwhelmed by the guests but delighted to meet such a distinguished company."

Nixon Presidential Library From left: Bebe Rebozo, Prince Philip and Richard Nixon

The letter continues: "After the brilliance of the other speakers and yourself, I am afraid my contribution was very lame and that night I woke up in a cold sweat when I realized I had forgotten to propose your health! I do humbly apologize."

Philip closed the letter to Nixon by remarking on the weather in New York ("horrible," he writes) and adding that he found "Miss Walters" to be "particularly charming and intelligent."

RELATED: Queen Elizabeth and Prince Philip's Untold Love Story — 'She Never Looked at Anyone Else'

Nixon Presidential Library From left: Queen Elizabeth, Prince Philip, Richard Nixon

Nixon Presidential Library

"I hope we did a good piece," the prince writes. "Again with very many thanks for your great kindness. Yours sincerely, Philip."

The Miss Walters mentioned is Barbara Walters, who interviewed Philip during his stay in New York. That interview lifted the curtain on life in the Queen's shadow, which Philip told Walters at the time was "awkward."

"You get used to anything," he told Walters when asked if he had settled into the role. "You'd be surprised."

Philip's path crossed with the Nixons on more than one occasion.

In 1957, Nixon, then vice president, and his wife welcomed both the Queen and Prince Philip to the U.S. Capitol on behalf of President Dwight Eisenhower. A decade later, in February 1969, then-President Nixon visited the Queen and Philip at Buckingham Palace and, the following year, the two couples met again in England at the U.K. prime minister's country residence.

Nixon reportedly had a special interest in the royal family, with Prince Charles later saying the president had attempted to set him up with first daughter Tricia Nixon.

RELATED VIDEO: Prince Charles Gets Emotional as He Views Public Tributes to Father Prince Philip with Camilla

Nixon Presidential Library From left: Queen Elizabeth, Prince Philip, Richard Nixon

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Philip's humor stayed with him "right to the end," according to former palace spokeswoman Ailsa Anderson, who recently told PEOPLE that the Duke of Edinburgh was "charming," with a "twinkle in his eye."

"When he spoke to you, you thought you were the only person who mattered in the world," Anderson said in PEOPLE's cover story. "It was like a lighthouse beacon shining onto you, and you feel like the only person he wanted to talk to."

Philip is set to be laid to rest at St. George's Chapel in Windsor Castle on Saturday amid strict COVID-19 guidelines.

According to Anderson, it's what the late prince would have wanted, even without the pandemic.

"Ironically, it is probably how he would have liked," she told PEOPLE. "No fuss, no bother. Right through his life, he never knew what all the fuss was about."

Watch: The wonderful life of Prince Philip, The Duke of Edinburgh