Queen Elizabeth II, decked out in a brilliant pink coat and matching hat, positively glowed as she greeted well-wishers in front of Windsor Castle on her 80th birthday.

Thousands had gathered for the event, crowded behind barricades as the Queen and her husband Prince Philip performed the annual walkabout beginning at about noon on Friday.

The Queen, smiling and appearing relaxed, exchanged greetings with her subjects, accepting flowers, cards and gifts during the 45 minutes the couple spent with the crowd.

Representatives of a number of youth groups presented cards and flowers to the Queen.

The crowd cheered and a military band played "Happy Birthday," as the Queen came out of Windsor Castle.

One loyal follower had camped out all night to greet the Queen, while others arrived later clutching red-and-white-and-blue Union flags, memorabilia and gifts.

She began the popular birthday walkabout tradition in 1970 during a tour of Australia and New Zealand.

In the days leading up to her birthday, she received 17,000 birthday greetings via email, and 20,000 cards in the mail. And on Friday she woke up to scores of well-wishers who had been gathering outside Windsor Castle since dawn.

She said the warm wishes helped make the day memorable.

"I have been very touched by what you have written and would like to express my gratitude to you all for making this day such a special day for me," she said in thanks of the many birthday cards and emails.

During a speech to The Empire Club in Toronto on Friday afternoon, Prime Minister Stephen Harper offered his warmest wishes to the Queen. He said he was impressed when he met her personally.

"I found her warm, gracious, intelligent, wise. I was also struck by her knowledge of this country, and her deep affection for Canada and its people," Harper said.

"She has been a model of selfless devotion and dignity for over half a century and I know we all look forward to the continuation of her reign for many, many years to come."

As Europe's longest-serving monarch and the official head of state and the Commonwealth, the Queen is more popular than ever.

A survey published this week found she is the most popular member of the royal family. The poll also found that more than half her subjects want her to remain on the throne for the rest of her life.

On Friday evening she was scheduled to attend a dinner at Kew Palace, hosted by her son, Prince Charles.

Early in the day, the celebrations kicked-off when a huge Royal Standard was raised from the highest point of Windsor Castle. The massive flag measures almost six metres by 12 metres, and is used for special celebrations.

Government buildings are flying the Union Jack in honour of the Queen's birthday, and an annual 21-gun salute was fired at 10:30 a.m. local time from a park near Windsor Castle. Soldiers in Hyde Park also blasted a special 21-gun salute.

During a ceremony to officially reopen the Gordon Highlanders Museum, Aberdeen, after a major refurbishment, Charles thanked the nation for their birthday wishes towards his mother.

"On this special 80th birthday of my mama I am most grateful to you for your kind wishes, which I shall certainly pass on this evening at dinner," he said.

Charles is also expected to broadcast a television tribute to his mother.

Margaret Kittle from Winona, Ont., made a last-minute decision to fly over for the celebrations. She was among those lining the royal route in Windsor, hoping to pass a personal greeting to the Queen.

"I came over specifically for it. I got the plane last night and took a cab straight from the airport. It was a last-minute decision and I have no regrets," she told Reuters.

School children, from four to nine years old and gripping miniature Union Jack flags, were lined up hours ahead of time to join in the singing of "Happy Birthday."

The Queen also received a special birthday greeting from 500 crew members aboard a Royal Navy aircraft carrier. The sailors lined up, spelling out 'Happy 80th' as a visual birthday tribute on the deck of the HMS Illustrious, while in the Red Sea en route to the Indian Ocean.

Prime Minister Tony Blair's Cabinet gave the Queen a China tea set worth about $2,000 Cdn.

The Queen also has an official birthday scheduled for June 17, when more outdoor festivities will be held.

Married with four children -- Charles, Anne, Andrew and Edward -- she was proclaimed the Queen in February 1952, and was crowned in 1953.

She took a vow to remain in the position for life, after her father, King George VI passed away. Many believe she has no plans of stepping down or handing over duties to Charles.