London and the rest of Great Britain is abuzz this weekend with four days of festivities to mark the the Queen's Diamond Jubilee.

In London, the Union Jack is everywhere, adorning everything from pubs to palaces, to celebrate the Queen's 60 years on the throne.

Festivities officially began Saturday with a 41-gun salute fired by the King's Troop, Royal Horse Artillery at Horse Guards Parade in central London.

The Queen and husband Prince Philip then arrived at Epsom Downs to attend the Epsom Derby, the U.K.'s richest horse race, with a purse of more than $2 million.

The 86-year-old monarch wore a violet-blue outfit and matching hat.

Welsh opera singer Katherine Jenkins led the crowd in singing the national anthem as the royal couple looked on.

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The Queen has a passion for horse racing and is a master breeder of horses. She has never won the Derby with one of her own horses and this year she does not have a horse in the race at all.

The Derby has been run for 233 years.

The Queen ascended to the throne in 1952 on the death of her father, King George VI, but she wasn't officially crowned until June 2, 1953.

Three days after her coronation, she went to the Derby to watch her horse Aureole race. Aureole came close to winning, but finished in second place.

1,000-boat river flotilla

For another big Jubilee event, boats are lining the Thames, the river that threads through the centre of the city. They'll  take part in what's being sold as a spectacular pageant set for Sunday when a 1,000-strong flotilla will take over, with the Queen heading the floating parade in a specially built royal barge.

"This really is a once-in-a-lifetime event," pageant master Adrian Evans said. "It hasn't happened for 350 years. It probably won't happen for another 350 years."

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Queen Elizabeth arrives for the Epsom Derby in southern England at the start of four consecutive days of Diamond Jubilee celebration. (Tom Hevezi/Associated Press)

Organizers may be wishing for a bit of magic to ward off the rains that are forecast for Sunday and into Monday.

Other celebrations include a concert Monday in front of Buckingham Palace featuring Elton John, Paul McCartney and Annie Lennox. Festitivies wrap on Tuesday with a with a religious service, a procession through the streets of London and the royal family's appearance on the palace balcony.

Canadians taking part

Cian Horrobin of Toronto is leading a trip to London sponsored by the Monarchist League of Canada, with 50 fellow travellers who are keen to acknowledge the Queen's contributions.

"After 60 years of dedicated service, it should be taken as a given that…Canadians would go to her in numbers that exceed the 50 that are in this group," Horrobin said. "For us to be here seems only appropriate considering how often she's come to us."

Horrobin's delegation will engage in some sightseeing before throwing themselves into the jubilee festivities, which begin in earnest on Sunday.

Horrobin and his group will attend a lunch hosted at Canada House before settling in on the banks of the Thames to watch the floating procession.

Horrobin said he will be up bright and early Monday morning to stake out a position at Buckingham Palace, scene of that day's special events.

Canda's Prime Minister Stephen Harper will travel to the United Kingdom to participate in jubilee celebrations from June 4-6.

In an interview with Sky News television on Friday, Prime Minister David Cameron paid tribute to the Queen's "extraordinary level of physical energy, mental energy, and above all devotion to her people, to the institutions of this country, to the way our democracy works."

Britain has had only one monarch celebrate a diamond jubilee before, Queen Elizabeth's great-great-grandmother, Victoria, in 1897.

Not everyone in Britain will be celebrating this jubilee The anti-monarchist group Republic plans a riverbank protest as the flotilla goes by on Sunday, followed by a pub night where royal refuseniks can drown their sorrows.

With files from The Associated Press and The Canadian Press