LONDON // Months of celebrations across the world will begin today as Britain's Queen Elizabeth II marks 60 years since she ascended to the throne.
Commonwealth countries from Australia to Zambia are staging diamond jubilee events, as well as hosting visits by members of the royal family as they criss-cross the globe during the year.
In Britain, celebrations will climax with a four-day national holiday in June, highlighted by a flotilla of more than 1,000 ships and boats travelling along the River Thames.
Yet the 85-year-old monarch will spend today doing what she has done almost every day since the death of her father in 1952. The agenda includes visiting King's Lynn Town Hall in eastern England and touring a nearby infants' school and nursery.
While Britain and the rest of the world have changed dramatically since the queen came to the throne after the death of her "beloved papa", King George VI, she has remained remarkably constant in her outlook and approach.
As one of her long-serving aides told the historian and royal biographer Ben Pimlott: "The queen's strength is that she doesn't change very much."
But her reign, which has overseen 11 British prime ministers and visits by 12 different US presidents, has not been without its traumas.
She endured what she described as her "annus horribilis" in 1992 after Prince Charles separated from Princess Diana; Prince Andrew, the Duke of York, split from Sarah Ferguson; Princess Anne divorced Capt Mark Phillips; and a severe fire destroyed part of Windsor Castle.
Five years later, she faced unparalleled criticism for appearing to be indifferent to the death of Princess Diana in Paris.
However, the Golden Jubilee celebrations in 2002 showed that the queen - Britain's longest serving monarch after Queen Victoria, who reigned for more than 63 years - still held a special place in Britons' hearts. The marriage of Prince William to Kate Middleton last year produced a surge in public affection for the monarchy.
Those sentiments are not shared in all the 15 nations where the queen remains head of state. Australia, in particular has a sizeable republican movement.
Royals embarking on jubilee sorties overseas include Prince Charles, who will visit Australia, Canada, New Zealand and Papua New Guinea; Prince William and his wife, who are heading to Malaysia, Singapore, the Solomon Islands and Tuvalu; and Prince Harry who will visit Belize, Jamaica and the Bahamas.
The queen's other sons, Prince Andrew and Prince Edward, the Duke of York and Earl of Wessex, will travel to India and the Caribbean, respectively, while the Princess Anne is to visit Mozambique and Zambia.
For the queen and her 90-year-old husband Prince Philip, there will be no foreign trips but a tour to various parts of the UK. The royal couple have been advised by doctors to take things a little easier following Prince Philip's minor heart surgery at Christmas.
As the queen has never given an interview since ascending to the throne, only those closest to her really know what gives her the drive to "carry on".
In a BBC TV documentary to be broadcast this week, Prince William describes his grandmother as "a professional" whose regal attributes include "her ability to know how to move around, who to speak to and how to engage with people within a few split seconds of meeting them".
Prince Harry, his brother, adds: "These are the things that at her age she shouldn't be doing, and yet she's carrying on and doing them. Not just in this country but all around the world."
Not everyone, though, is getting caught up in diamond jubilee fever. The campaign group Republic, which wants the monarchy abolished, is planning a series of demonstrations to coincide with 60th anniversary events, including a protest during the Thames flotilla.
Graham Smith, a spokesman for the group, said: "The pageant goes to the heart of what's wrong with the monarchy. It's an enforced celebration of hereditary power, and all the problems that spring from it."