* Queen Elizabeth marks 60 years on throne
* Big crowds expected over four-day celebrations
* Monarch, at 86, seen as symbol of stability
By Mike Collett-White and Michael Holden
LONDON, May 25 Britain's Queen Elizabeth will celebrate 60 years on the throne next month along with huge crowds expected for a pop concert at Buckingham Palace, a grand procession through the streets of London and a 1,000-strong flotilla along the River Thames.
The Diamond Jubilee comes just over a year after the royal wedding of Prince William, the queen's grandson, to Kate Middleton, a spectacular display of pomp and pageantry which has boosted the monarchy's popularity at home and abroad.
While international media attention has focused on the young Duke and Duchess of Cambridge since their marriage, in early June it is the queen who will be in the limelight as she becomes only the second British monarch to mark the milestone.
Queen Victoria also made it to 60 years in 1897, although the vast British Empire she reigned over at that time has all but vanished and royalty has become a largely symbolic institution with few real powers.
The queen has less than four years to go to become the longest serving British monarch, but she trails Thailand's King Bhumibol Adulyadej as the longest-serving living head of state.
Despite her age, courtiers and many commentators believe that 86-year-old Elizabeth remains an important figurehead in Britain and beyond, a symbol of stability and service that has taken on added weight during straitened economic times.
A poll published in Britain's Guardian newspaper on Friday showed public support for the queen was at a record high in spite of harsh economic times and growing cyncism towards politicians following a number of high-profile scandals.
The survey showed 69 percent of respondents thought Britain would be worse off without the monarchy, with 22 percent saying it would be better off - the largest margin between the opposing views since the poll was first commissioned in 1997.
"Historically people have turned to symbols of certainty, probity and solidity in times of crisis," said Robert Hardman, author of a recent biography of the monarch called "Our Queen" and a writer for the royal-friendly Daily Mail.
"People feel she's lived through all sorts of crises, not least the Second World War, and she's dependable."
Members of the royal family have been marking the jubilee all year with tours both national and international, but the climax of the celebrations is a four-day weekend from June 2-5.
On Saturday, the queen indulges her life-long passion for horses with a visit to the Epsom Derby.
Sunday has been billed "The Big Jubilee Lunch" encouraging thousands of Britons to spill out on to the streets and share a meal with neighbours and friends.
Also on Sunday, arguably the most spectacular event takes place on the River Thames snaking through central London.
Up to 1,000 vessels from around the world will assemble to accompany the queen and her husband on the Royal Barge as they travel along the river, watched by a flag-waving, cheering crowd expected to number more than a million.
Paul McCartney and Elton John are among the artists set to perform at a pop concert outside Buckingham Palace on Monday, when a network of 2,012 beacons will also be lit across Britain and the Commonwealth of mostly former British colonies.
On Tuesday, the jubilee weekend concludes with a service of thanksgiving at St. Paul's Cathedral and a short carriage procession from Westminster to Buckingham Palace where the queen and her family will appear on the balcony.
Unlike the younger generation of royals whose status borders on that of celebrities, the queen has been a quieter, less splashy presence.
If anything, she may suffer from over-familiarity in the eyes of the British public, which sees her face on coins and stamps and in countless photographs of her in colour-coordinated outfits while on official visits.
"We slightly overlooked the fact that she's done it for 60 years and suddenly realised that that's a great achievement," Hardman told Reuters.
"The jubilee coincides with a marked revival in interest in the royal family -- it's been a very good few years for them and not just because of the royal wedding."
MEDIA MESMERISED, POLLS UNCLEAR
Much of the British media and many broadcasters from the United States and beyond have given the monarchy overwhelmingly positive coverage in recent years, particularly since the 2011 wedding which was watched by up to two billion people worldwide.
Royalists say opinion polls such as the one in the Guardian have consistently shown solid support for the monarchy among the British public.
The republican movement, which has struggled to find a voice during the recent resurgence in royal interest, argues that the statistics tell a different picture.
Anti-monarchist group Republic quoted findings last month showing only 41 percent of Britons believed the royal family was a unifying force with 32 percent saying it made no difference.
Stephen Haseler, a prominent academic and critic of the monarchy, called the jubilee plans "unbelievable" at a time when the country was in a recession.
"This is Disneyland," he told Reuters. "She (the queen) is going to come down the River Thames in a barge, for God's sake, with all kinds of fireworks. This is kids' stuff, this is what you take kids to Disneyland to see and it's our head of state.
"You should be more dignified in a really serious recession. You ought to cut down on this nonsense. It's making us a bit of a laughing stock. What have we got to celebrate?"
The royal family officially costs taxpayers between 30 and 40 million pounds a year ($47-63 million), although the total does not include security and other outgoings. Republic estimates the cost at over 200 million pounds.
UPS AND DOWNS
Elizabeth was in Kenya with husband Philip when she learned of the death of her father, George VI, famously portrayed by Colin Firth in the Oscar-winning movie "The King's Speech".
Still in her mid-20s, she returned home to be greeted at the airport by Winston Churchill, one of 12 prime ministers to have served during her reign.
In 1953 her coronation in Westminster Abbey was televised for the first time and watched by millions of people globally.
Even her most ardent admirers admit that her reign has had its ups and downs, despite her image as a constant in a rapidly changing world.
The queen famously described 1992, marked by royal divorce, separation and a fire at Windsor Castle, as her "annus horribilis", yet things were to get worse.
In 1997, a year after divorcing heir-to-the-throne Prince Charles, the wildly popular Princess Diana was killed in a high speed car crash in Paris, dealing a serious blow to the royals.
The following decade, which included an enthusiastically celebrated golden jubilee in 2002 and the deaths of her mother and sister in the same year, saw the queen's public standing rebound.
The majority of commentators believe that while the queen is alive, the monarchy is unlikely to face a serious crisis.
That could change when her son Charles accedes the throne, some argue, because he is regarded as less predictable and diplomatic. William and Kate would be popular as king and queen, but they could have a long wait ahead.
(Reporting by Mike Collett-White)