Prince William, as second-in-line to the throne, will one day be head of the armed forces. Before that happens, he has chosen to join younger brother Harry for officer training at the Royal Military Academy at Sandhurst.
Prince William will one day be head of the armed forces
The start of his military career came after several months' work experience, during which he shadowed financial staff in the City of London, acted as a "rescue novice" with a mountain rescue team and learned about land estate management.
Born William Arthur Philip Louis in London on 21 June 1982, he was soon introduced to the public with the first official photographs.
He went to Jane Mynors' nursery school in London in September 1985 and two years later started at Wetherby School.
He moved to Ludgrove School in Berkshire in September 1990 where he stayed until entering Eton in 1995.
In that year, Prince Charles struck a deal with the press whereby William and Harry were left alone in return for limited access at press and photo calls.
Miss Middleton and Prince William met at university
William left Eton with A-levels in geography, biology and history of art as well as 12 GCSEs.
During a gap year between school and university he went to Mauritius, spent time in Africa, trekked with the Army in Belize and worked as a Raleigh International volunteer in Chile.
But it was, he says, his short stint working as a labourer on a dairy farm in south-west England that he enjoyed the most.
William met and shared a cottage with his girlfriend, Kate Middleton, while they were undergraduates at St Andrew's University in Fife, Scotland.
Following the Asian tsunami in December 2004, he and Harry helped raise £40,000 for survivors by playing in a charity polo match.
The brothers were also shown working as volunteers at a Red Cross centre, putting together aid packages for those affected.
In 1997, the world watched William grieve for his mother
In June last year William graduated with a class 2:1 degree in geography, making him one of the most academically successful royals. Later that month he passed examinations for Army officer training at Sandhurst.
In July, he flew to New Zealand to meet the touring British and Irish Lions rugby union team.
While there, William also carried out his first solo engagements, attending ceremonies in Wellington and Auckland on behalf of the Queen to mark the anniversary of the end of World War II.
In September he became patron to young people's homelessness charity Centrepoint, following in the footsteps of his mother Diana Princess of Wales, who represented the charity from 1992.
Although William is now 23, there is still much sympathy for the loss of his mother in a car crash when he was 15.
Many people clearly remember him walking behind the cortege of his mother at her funeral in Westminster Abbey in 1997, accompanied by his brother, father, grandfather and uncle.