British Queen celebrates 90th birthday

Queen Elizabeth II attends a celebration to mark the 500th anniversary of the Royal Mail postal service at the Royal Mail Delivery Office in Windsor, western London, Britain, on April 20, 2016. Queen Elizabeth II is set to celebrate her 90th birthday on April 21. (Xinhua/Han Yan)

LONDON, April 21 -- Gun salutes took place across Britain Thursday to celebrate the 90th birthday of its longest reigning monarch.

Well-wishers from across the world gathered outside the Windsor Castle and the town to celebrate the 90th birthday for Queen Elizabeth II.

Some people even camped out overnight so that they could get a better spot to see the Queen, local media said.

Prince Charles paid his tribute to his mother through a special radio broadcast on Thursday morning, in which he read an edited passage from William Shakespeare's King Henry VIII.

British Prime Minister David Cameron said: "Her Majesty has devoted her entire life to the service of others representing our country, and carrying out all her duties with extraordinary grace and humility. Rarely has anyone in public life served for so long, served so brilliantly, worked so hard, and brought so many people together."

"And in this modern Elizabethan era, in which so much around her has changed, Her Majesty has been steadfast, a rock of strength for our nation, for our Commonwealth, and on so many occasions, for the whole world. She is our Queen and we could not be more proud of her," Cameron said.

The Queen earlier said on twitter that "I send my best wishes to those who are celebrating their 90th birthday ... on this shared occasion, I send my warm congratulations to you."

Accompanied by Prince Philip, the Queen arrived at Windsor Castle at noon, met people there and then walked through the streets of Windsor. The crowds were singing Happy Birthday to her.

The Queen came to throne in 1952. She celebrates two birthdays each year, one is the day she was born on April 21, and another is an official birthday in June.

A range of splendid celebrations will be held in the grounds of Windsor Castle from May 12 to 15, as well as from June 10 to 12.