AS the Queen and Prince Philip settle in at Windsor Castle to quietly celebrate their platinum wedding anniversary on Monday, it is yet another landmark for our longest-reigning monarch.

Princess Elizabeth, as she was at the time, married dashing naval officer Lieutenant Philip Mountbatten at London’s Westminster Abbey on November 20, 1947, just two years after the end of the Second World War, in a lavish ceremony attended by statesmen and royalty from around the world. Seventy years on, the Queen, 91, and her 96-year-old husband will mark their platinum anniversary with a small family party at the Castle.

Buckingham Palace said there would be no public event to mark the occasion.

Sunday also sees the 70th anniversary of Philip being made a Knight of the Garter King George VI. The Queen was made a Knight eight days before, an anniversary much overlooked, one source told me.

Greek-born Philip, a descendant of Elizabeth’s great-great-grandmother Queen Victoria in his own right, has been at his wife’s side throughout her 65-year reign. He was the person who broke the news to her in 1952 that her father, King George VI, had died and that she was now Queen.

“One of the secrets of this very, very long marriage, and it’s an incredibly impressive anniversary, is the fact Prince Philip has always seen it as his main duty to support the Queen, to help her in whatever way he can,” royal historian Hugo Vickers told me. “It think they are an incredible team. One of the reasons is that they continue to serve Britain and enjoy it. The Queen still rides and Philip carriage drives regularly still.”

The couple first met when they attended the wedding of Prince Philip’s cousin, Princess Marina of Greece, to Elizabeth’s uncle, the Duke of Kent, in 1934. Philip then gained the attention of his future wife when the then-13-year-old princess made a visit with her parents to the Royal Naval College at Dartmouth, Devon, where he was a cadet.

“She was truly in love from the very beginning,” the queen’s cousin Margaret Rhodes, a life-long friend and one of her bridesmaids who died last year, wrote in her memoir.

Their engagement was announced in July 1947 and they married four months later. With Britain still recovering from the war, the wedding offered a rare burst of colour and pageantry against an austere background of rationing and shortages.

The 21-year-old princess, who wore an ivory silk Norman Hartnell gown decorated with 10,000 seed pearls, had to collect coupons for her dress like other post-war brides and the couple spent their honeymoon in southern England and Scotland.

While some two billion people were estimated to have watched the couple’s grandson Prince William marry his wife Kate in 2011, their own wedding was only broadcast live to some 200 million radio listeners, although highlights of the day were captured on grainy black and white film footage.

It was at the couple’s 50th wedding anniversary in 1997 that the queen paid a rare personal tribute to her husband.

“He has, quite simply, been my strength and stay all these years,” Elizabeth said.

No other British monarch has celebrated such a landmark, and indeed Elizabeth was the first to mark a diamond wedding anniversary in 2007.

Philip, who has suffered health issues recently,in recent years and was hospitalised in June, retired from active public life in August. They both attended Remembrance Day, although a royal source said the monarch had decided not to lay a wreath so she could watch from a nearby balcony alongside Philip.

“Without Prince Philip the queen would have had a very tough and lonely life. He’s been a complete support to her, a rock to her, from the moment she was on the throne,” royal biographer Claudia Joseph has said.

The Observer today publishes just some of the thousands of pictures of the couple taken during their 70 years together – a marriage that has more than stood the test of time.