The Queen's life will be celebrated today with a national service of thanksgiving that will launch a weekend of events marking her 90th birthday.
At St Paul's Cathedral leading figures from national life will gather to honour the Queen's milestone with prayers, hymns and readings.
Among the congregation will be senior members of the Royal Family including the Duke of Edinburgh, Prince of Wales, Duchess of Cornwall, Duke and Duchess of Cambridge and Prince Harry.
Politicians past and present, diplomats and governors-general will also be in the congregation.
Prime Minister David Cameron will read from the New Testament and the Archbishop of Canterbury will preach the sermon.
Prince Philip celebrates his 95th birthday, the Queen's consort was born on June 10, 1921, and his milestone will be marked with traditional gun salutes.
Philip continues to be a constant presence at the side of the monarch during many of her official duties and he carries out hundreds of public engagements in his own right.
A double portrait of the royal couple taken by celebrity photographer Annie Leibovitz has been released to mark the Queen's birthday.
The thanksgiving service is the start of a weekend of major events staged to honour the Queen's 90 years.
On Saturday spectators will see the traditional pomp and military splendour of Trooping the Colour - also known as the Queen's Birthday Parade - and on Sunday a street party for 10,000 revellers will be staged in The Mall with other smaller events across the country.
The St Paul's Cathedral service will also feature Sir David Attenborough and Paddington Bear creator Michael Bond, who, like the Queen, both turned 90 earlier this year.
The popular natural history broadcaster will read a reflection on the passing of the years written by the famous children's author who created the Paddington Bear series of books.
Hilda Price, a 90-year-old widow who shares her birthday with the Queen, is one of six individuals given the honour of leading prayers, specially written to mark the Queen's 90 years, which will include a reference to the Duke's 95th anniversary.
Mrs Price, who lives in Cardiff, said "It was the shock of my life'' when she was told she had been picked to take part in the service.
The great-grandmother was born on the same day as the Queen and in the same year - April 21, 1926 - but the two women have lived very different lives.
Mrs Price was born in a house in Carmarthen, while the Queen was born in a town house in London's Mayfair, and grew up to become the wife of the Reverend Ken Price who served in a series of parishes in the Welsh valleys and surrounding areas.
Other members of the Royal Family due to attend the service are the Duke of York and his daughters Princess Beatrice and Princess Eugenie, the Earl and Countess of Wessex and their children Viscount Severn and Lady Louise Mountbatten-Windsor.
Also attending will be the Princess Royal and Vice Admiral Sir Tim Laurence, Duke and Duchess of Gloucester, and Duke and Duchess of Kent.
After the service the Queen, joined by Philip, Charles and Camilla, will host a lunch for visiting governors-general at Buckingham Palace.
And William, Kate and Harry, and other members of the Royal Family will attend a reception at the City of London's Guildhall for members of the congregation.