Queen Elizabeth II marks longest reign -- by doing her job

The United Kingdom's Queen Elizabeth II marked the day she became the longest-serving monarch in her nation's history – by doing her job.

On the day when she surpassed Queen Victoria, who served for 63 years and seven months on the throne, the beloved 89-year-old monarch carried on her ribbon-cutting routine as usual, traveling to open a new railroad in Scotland.

Dressed in one of signature pastel outfits – this one a two-tone turquoise number – Elizabeth rode by train from the Scottish capital, Edinburgh, to Tweedbank in southern Scotland, where she opened the just-built Borders Railway.

The queen waved to crowds at Waverley Station in Edinburgh as she boarded a train bound for the opening ceremony. The arrival of her helicopter had been delayed by fog.

Elizabeth, who is concluding her usual summer vacation at Balmoral, her baronial castle in Scotland, spoke briefly — very briefly — at the ceremony, telling the audience that her new title was "not one to which I have ever aspired," according to the BBC.

Still, she was heartened by the worldwide outpouring of congratulations from the high and mighty down to the small and slight.

"Inevitably a long life can pass by many milestones — my own is no exception — but I thank you all and the many others at home and overseas for your touching messages of great kindness," she said.

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Elsewhere, the milestone was marked more definitively. In London, a flotilla of historic vessels, leisure boats and ferries took part along the River Thames in central London. The HMS Belfast sounded a four-gun salute.

And Prime Minister David Cameron told the nation that though the queen wanted the day to go on like any other that millions of Britons would be celebrating.

"While I rarely advocate disobeying Her Majesty, least of all in her own Parliament," he said in speech at the House of Commons, "I do think it's right today we should stop and take a moment as a nation to mark this historic milestone and to thank Her Majesty for the extraordinary service she's given to our country over more than six decades.

"Over the last 63 years, Her Majesty has been a rock of stability in a world of constant change, and her selfless sense of service and duty has earned admiration not only in Britain, but right across the globe," Cameron added.

A former prime minister, John Major, also praised the queen's long reign as a comfort to Britons.

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"Whilst prime ministers have come and gone, celebrities have come and gone, life has changed, she and the monarchy have been an absolute constant in their lives, and I think that is very reassuring," he said.

British legislators planned to mark the milestone in Parliament and newspapers were filled with special souvenir tributes to the queen.

Queen Elizabeth II's historic reign marked by photographer Mary McCartney

Buckingham Palace marked the event by releasing an official photograph of the queen taken by Mary McCartney, a photographer who is the daughter of former Beatle Paul McCartney.

Elizabeth came to the throne in 1952 upon the death of her father, King George VI.

The Associated Press contributed to this report.