Five days of celebrations wound up with a further tribute for Elizabeth ll in a church service, where the Queen was hailed for giving Britons a "sense of calmness, serenity and stillness" in a turbulent world.
During the special thanksgiving service, the Queen has also been praised for giving the nation "heart,” taking account of the Queen's role as Head of the Church of England, a position she deeply cherishes.
A special birthday prayer written for the occasion began the proceedings in the ornate 15th century chapel as voices of the choir filled the historic building.
The Rt Reverend David Conner, the Dean of Windsor, paid tribute to the monarch's "sense of calmness, serenity and stillness" in his sermon at St George's Chapel.
He singled out the Queen's Christian faith, saying it was the "very bedrock" of her life.
"On this particular St George's Day, in St George's Chapel, family and friends and neighbours have gathered to join in thanksgiving for the birthday of our Queen," Bishop David told the congregation, which included senior royals, friends of the monarchy and staff."As we do so, I have a hunch that every one of us will be expressing gratitude, for some kind of encouragement received as we have tried, in our ordinary lives, to be decent and to care.
"Your Majesty, not so much through word as by unselfconscious good example, you encourage us; you give us heart."
Among the 700 guests were former prime ministers Baroness Thatcher and Sir John Major, Earl Spencer, the brother of Diana, Princess of Wales, and the Agha Khan.
An anthem by the Poet Laureate Andrew Motion was also performed. "The Golden Rule", written as a birthday tribute, was sung by the choir and set to music by the Master of The Queen's Music Sir Peter Maxwell Davies.
The Queen Elizabeth II was proclaimed queen in February 1952, aged just 25, after the death of her father, King George VI, and was crowned in June 1953.
