The Queen's 90th birthday is fast approaching and soon the nation will celebrate the milestone of its longest-lived monarch.
The big day on April 21 will be a moment of personal happiness for the Queen, who will have a dinner staged in her honour by her family.
But the joy will also be shared by the nation, with thousands expected to attend celebrations, planned for the summer, to mark the occasion.
Over a weekend in June a series of events will be staged from a St Paul's Cathedral service of thanksgiving to the traditional Trooping the Colour ceremony, also known as the Queen's Birthday Parade.
The Queen is said to be excited by the prospect of 10,000 guests joining herself, the Duke of Edinburgh, the Duke of Cambridge and Prince Harry in The Mall for a sit-down celebration.
Called the Patron's Lunch it will honour the monarch's lifetime dedication to service and will be the culmination of the weekend, with communities across the country encouraged to hold local street parties.
When the Queen became the nation's longest-reigning monarch last autumn - passing Queen Victoria's record - she remarked that living to a ripe old age can bring many anniversaries: "Inevitably a long life can pass by many milestones. My own is no exception."
And in her Christmas broadcast the Queen made a light-hearted remark about turning 90, hinting she was aware of the significance of the milestone: "I am looking forward to a busy 2016, though I have been warned I may have Happy Birthday sung to me more than once or twice."
During her 64-year reign the monarch has been served by 12 prime ministers from Sir Winston Churchill to David Cameron, while Barack Obama is the 12th US president to hold office over the same period.
Over the decades Britain has undergone major transformations from technological advances like computers and supersonic flight to developments in society and the political landscape.
Her personal life has brought her happiness with the Queen, who acceded to the throne at the age of 25, now surrounded by her children, grandchildren and great-grandchildren.
But she endured her ''annus horribilis'' in 1992, the year the Prince of Wales separated from wife Diana, the Duke of York split from Sarah, and the Princess Royal divorced Captain Mark Phillips.
The woman who is seen by many as a stabilising force in national life was never expected to be Queen when she was born on April 21, 1926 in a town house in London's Mayfair, the first child of the Duke of York, later King George VI.
Her destiny was changed with the abdication of her uncle, Edward VIII, for the woman he loved - American divorcee Wallis Simpson.
Famously the Queen dedicated her life to her future role as monarch on her 21st birthday - vowing to serve the Commonwealth: ''I declare before you all that my whole life, whether it be long or short, shall be devoted to your service and the service of our great imperial family to which we all belong.''
On the day of her birthday the Queen will step out of her Windsor Castle home and go on a walkabout in the town centre, meeting the crowds who are expected to gather and are likely to sing her Happy Birthday.
Other royal engagements are planned for the period, but the seal will be set on the special day the moment well-wishers reach out to shake the Queen's hand and offer their congratulations.