LONDON, United Kingdom (AFP) — Queen Elizabeth II celebrated 70 years of marriage on Monday to the man she calls her “strength and stay”, making them Britain’s first reigning couple to mark a platinum wedding anniversary.

The bells of Westminster Abbey, where Elizabeth married Prince Philip on November 20, 1947, rang out to mark the seven decades of the royal union.

The two were on a visit to Kenya when Elizabeth found out she had become queen following the death of her father king George VI in 1952. She has since gone on to become the nation’s longest serving sovereign.

Prime Minister Theresa May led the congratulatory tributes to the royal couple.

“They have devoted their lives to the service of the UK and the Commonwealth — my best wishes to them both on this special occasion,” she said.

At their 50th wedding anniversary in 1997, Elizabeth paid tribute to Philip, Duke of Edinburgh, saying: “He has, quite simply, been my strength and stay all these years.

“I, and his whole family, and this and many other countries, owe him a debt greater than he would ever claim, or we shall ever know,” she said.

She has also described the prince as her “rock”.

Official photographs have been released for their anniversary, along with a set of commemorative stamps documenting their engagement, wedding and honeymoon.

One of the photographs shows them in front of Thomas Gainsborough’s 1781 portraits of George III and Queen Charlotte, whose 57-year union is the next longest British royal marriage.

In another photograph, the Queen poses in the same cream dress she wore at her diamond wedding anniversary thanksgiving service 10 years ago, along with a yellow gold, ruby and diamond brooch Philip gave her in 1966.

The royal couple will not hold any public events but have invited family and friends to Windsor Castle for a private dinner on Monday evening.

The fairy-tale royal wedding in 1947 was a morale boost during the tough years immediately after World War II.

Their marriage endured, as Philip accepted living in his wife’s shadow, and the Queen seemingly forgiving his periodic gaffes.

They had four children — Charles, Anne, Andrew and Edward — whose marriages have been less successful, with all except Edward having divorced.

The couple also boast eight grandchildren and five great-grandchildren, with a sixth great-grandchild expected in April, when Prince William and wife Kate Middleton’s third child is due. The 96-year-old Duke of Edinburgh retired from the public eye this summer, enjoying his newfound free time reading and painting.

For her part the Queen, at 91, is slowly passing over some of her official duties to her son Prince Charles, now aged 69.

The royal couple first met as teenagers, and eventually married when Elizabeth was a 25-year-old princess.

Philip, the son of a Greek prince banished from that country, renounced his titles and Greek Orthodox faith and became a British citizen in order to marry, adopting his mother’s anglicised name, Mountbatten.

Prior to the wedding he told the Queen Mother he had “fallen in love completely and unreservedly” with her daughter.