Britain celebrated Queen Elizabeth II's 90th birthday and her service to the country Friday with solemn pomp, pageantry and prayer at St. Paul's Cathedral ahead of a weekend of festivities.

The Archbishop of Canterbury, Justin Welby, set the tone by reminding Britain of the queen's long life and dedicated service. In essence, he said the nation was lucky because Elizabeth only became queen by chance.

"We look back on Your Majesty's 90 years in the life of our nation with deep wonder and profound gratitude," he said. "Through war and hardship, through turmoil and change, we have been fearfully and wonderfully sustained."

The celebration has been a lengthy affair, starting with her real birthday in April. The monarch's official birthday is traditionally celebrated in June when Britain's weather can be more favorable.

The monarch, dressed in primrose yellow coat-dress and matching hat, and her husband Prince Philip attended a service of thanksgiving at St. Paul's Friday, on what is Philip's 95th birthday.

She turned to smile at a crowd of well-wishers singing "Happy Birthday" as she climbed the cathedral steps.

Among those offering tribute was the popular naturalist and broadcaster David Attenborough, who read a short story by Paddington Bear creator Michael Bond. Both men turned 90 this year and attended the service.

Prince Charles and his wife Camilla, Prince William and his wife Kate, Prince Harry and dozens of other royals joined politicians and the wider community in a thundering rendition of "God Save the Queen.

The traditional Trooping the Color parade will be held Saturday, the queen's official birthday. The event is expected to draw throngs of Britons and visitors to Buckingham Palace for a possible balcony appearance by the senior royals.

On Sunday, the Mall in front of the palace will host lunch for roughly 10,000 charity workers, patrons and members of the royal family.

Street parties are planned in many locations, including some in Commonwealth countries and also in the United States.

British newspapers have been filled with paeans to the queen, and editorials urging the public to show its gratitude for her long reign.

Philip, who has heart disease, missed an engagement recently due to health issues but is expected to participate throughout the weekend.

After the three-day extravaganza, the queen is expected to turn her attention to the horse racing season and her lengthy summer holiday in Scotland.