King Charles is one of many world leaders to send condolences upon learning of the death of former U.S. President Jimmy Carter.

Carter, the longest-living U.S. president and a Nobel Peace Prize winner, died at age 100 on Dec. 29 at his home in Plains, Georgia. His final public appearance was over a year prior, when he mourned the death of his wife, Rosalynn Carter, in November 2023. She was 96.

“It was with great sadness that I learned of the death of President Carter,” King Charles wrote Dec. 29. “He was a committed public servant, and devoted his life to promoting peace and human rights. His dedication and humility served as an inspiration to many, and I remember with great fondness his visit to the United Kingdom in 1977.”

“My thoughts and prayers are with President Carter’s family and the American people at this time,” added the King, 76. The message concluded with “Charles R.,” indicating that the message came from the King himself.

King Charles and Jimmy Carter met only once — at the G7 Summit in London in 1977. That same year, Carter visited Buckingham Palace to meet with Queen Elizabeth and Prince Philip — and had a now-infamous interaction with the Queen Mother.

Carter — who served as president from 1977 to 1981 — had dinner with the royals at the palace following a NATO Ministerial Meeting at Lancaster House in London, according to the White House Historical Association. When Carter went to say goodbye to the Queen Mother at the end of the night, it has been reported that Carter broke royal protocol and gave her a peck on the cheek, as opposed to the customary curtsy. At the time, the British media claimed the Queen Mother said the president kissed her on the lips.

“He is the only man since my dear husband died to have had the effrontery to kiss me on the lips,” the Queen Mother reportedly told her biographer, according to Town & Country. Her husband, King George VI, had died unexpectedly 25 years prior in 1952 at just 56 years old.

“I took a sharp step backwards — not quite far enough,” the Queen Mother also reportedly said of the encounter.

Carter addressed the moment in his autobiography A Full Life: Reflections at 90, calling the British media’s description of the kiss upsetting, writing that he only gave her a kiss “lightly on the cheek” following dinner.

“More than two years later, there were reports in the British papers that grossly distorted this event, stating that I had deeply embarrassed her with excessive familiarity,” Carter wrote. “I was distressed by these reports, but couldn’t change what had happened — nor did I regret it.”

Carter maintained a friendly relationship with the royal family, and when Queen Elizabeth died at age 96 on Sept. 8, 2022, Carter expressed his own condolences, writing that “Rosalynn and I extend our condolences to the family of Her Majesty Queen Elizabeth II and the citizens of the United Kingdom. Her dignity, graciousness and sense of duty have been an inspiration, and we join the millions around the world in mourning a remarkable leader.”

When Carter turned 100 years old on Oct. 1, PEOPLE understands that the King “expressed warm personal greetings and great admiration” for Carter’s lifetime of duty and public service, according to a spokesperson for the monarch. In a private message, the King congratulated Carter on becoming the first former president to become a centenarian.

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Carter entered hospice care nearly two years ago, in February 2023, and leaves behind four children, 11 grandchildren and 14 great-grandchildren.

“He has had a very full, wonderful, productive life,” his cousin Betty Pope told PEOPLE. “He wanted to make sure every day of his life he was able to do what he was charged to do personally — which, he felt, was to try to make peace and improve the world.”