After showing a united front against rumors of a marital rift, the Queen and Prince Philip marked a decade of marriage at home with dinner and gifts (among them, a tin tea kettle)
queen elizabeth and prince philip
After his tour at sea, Prince Philip reunited with Queen Elizabeth in Portugal, 1957.
| Credit: Daily Mirror/getty

"I'd love to know their secret . . . because they are the most lovely couple," Prince William said of Queen Elizabeth and Prince Philip in 2016, when his grandparents had been married 68 years. (The royal couple, who wed in 1947, would go on to toast six more anniversaries before Philip's death at age 99 earlier this month.)

As William marks 10 years of marriage to Kate Middleton (which PEOPLE is commemorating in a new special edition William & Kate: 10 Joyous Years), he might consider what the Queen and Prince Philip's lifelong union looked like, back when they were approaching the same milestone. It wasn't the easiest year for the young couple, but they had faced its challenges together.

By 1957 the Queen and her husband, the Duke of Edinburgh, were the parents of two young children, Charles and Anne, and Elizabeth had ascended to the throne following her father's unexpected death at age 56. She and Philip were still working out a balance between private and public life when rumors prompted Buckingham Palace to take the unusual step of issuing a statement, reading: "It is quite untrue that there is a rift between the Queen and the Duke."

Queen Elizabeth and Prince Philip on their honeymoon in 1947
| Credit: Central Press/Getty

In October 1956 Philip had begun a four-month ocean tour to open the Melbourne Olympics and visit several Commonwealth countries. It meant spending his ninth wedding anniversary, as well as Christmas and New Year's, at sea while his wife remained in England. Also aboard the Britannia was Philip's longtime friend and private secretary Michael Parker, who, before the ship returned home, was sued by his wife, Eileen, on grounds that he had been unfaithful during the voyage. The suggestion that the royal yacht was a floating den of sin proved irresistible, particularly to some the U.S. press, who speculated that the trip had caused trouble in the royal marriage.

Those stories resurfaced in 2017 when season 2 of the Netflix series The Crown dramatized the episode. "People have said, 'He must have been unfaithful,' but there is no solid evidence for that," Robert Lacey, the historical consultant on The Crown, told PEOPLE at the time. What the show did get right was Elizabeth's determination to have her marriage succeed. "The Queen was the model of discretion and made absolutely clear that Prince Philip is the only man she has ever loved," Lacey says today. Her relationship with Philip was then, as it was until their final days together, "based on a foundation of absolute love."

Prince Philip, Queen Elizabeth
Prince Philip and Queen Elizabeth
| Credit: Countess of Wessex

Philip and Elizabeth reunited in Portugal when his tour ended in February 1957. Soon after, she officially dubbed him a prince of the United Kingdom. (Unable to let the rumors go, some papers speculated that the elevated title would shield Philip from having to testify at the Parkers' divorce trial.)

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Ahead of the couple's tour of North America in the fall of 1957, Philip appeared solo on the cover of Time magazine. The accompanying story offered a glimpse into the lives of what the magazine called Britain's busiest married careerists: "At the start of each busy day, the door between their adjoining bedrooms at the palace is invariably open to permit them to chat while dressing. Even on the most crowded days they try to keep the time between 5 and 6:30 each evening free for a family romp with 7-year-old Anne (and Prince Charles when he is not at school); the rare evenings they can spend alone together are frequently devoted to television and an exchange of mocking criticism when one or the other of them appears on the screen."

queen elizabeth and prince philip

For more, pick up PEOPLE's tribute issue, Prince Philip: The Lifelong Love Story of Queen Elizabeth and the Duke of Edinburgh, available now wherever magazines are sold.

In Canada, Elizabeth appeared newly confident as she became the first reigning monarch to open Parliament there. Then it was on to the U.S., where President Dwight D. Eisenhower hosted the royal couple at the White House. Back at home, their Nov. 20 anniversary was a private affair, but Time reported there was a dinner party, and gifts from Philip included a piece of jewelry he had designed, white carnations, and a tin kettle, a joking nod to the traditional material honoring a decade of matrimony. They were just 31 and 36 at the time, with so much ahead, including the births of sons Andrew and Edward, weddings, grandchildren and great-grandkids. They were, says Lacey, "partners in life."