The Queen granted the BBC unprecedented access to hundreds of home-made recordings shot by her, her parents and the Duke of Edinburgh in honour of her upcoming Platinum Jubilee.
The home movies, which had been held privately by the Royal Collection in the vaults of the British Film Institute, capture the Queen's life from being pushed in a pram by her mother to her coronation in 1953.
The 75-minute documentary, titled Elizabeth: The Unseen Queen, captures the first extended visit of Prince Philip to Balmoral in 1946 while the couple's engagement was still not public.
It depicts a beaming Princess Elizabeth showing the camera her engagement ring.
The Queen, 96, was a young princess when she first met naval cadet Prince Philip of Greece in 1939, during a visit to the Royal Naval College in Dartmouth where he was studying.
Philip, who was just 18, was introduced to 13-year-old Elizabeth at the house of the captain of the college.
The pair began writing to each other and Philip was invited to spend the Christmas of 1943 with the royal family at Windsor.
It has previously been suggested the couple became unofficially engaged in the summer of 1946 while they were staying at Balmoral but the official announcement was delayed until after Princess Elizabeth reached the age of 21 and returned from a royal tour of South Africa the following year.
The couple married in November 1947 and were married for 73 years before the Duke of Edinburgh died in April 2021, just a few months before his 100th birthday.
The BBC documentary will depict rare moments including footage of Princess Elizabeth with her uncle Prince George The Duke of Kent, who died in a plane crash in 1942 while on active service, and King George VI's last visit to Balmoral in 1951.
It will also show her as a young mother to Prince Charles and Princess Anne.
BBC Studios reviewed more than 400 reels of film, discovering lost newsreel and behind the scenes recordings of state events, believed to have been privately commissioned by the royal family.
Filmmakers listened to more than three hundred of the Queen's speeches, spanning over eight decades, to make the film which will be narrated by the Queen's own voice and words alongside newsreel audio.
Simon Young, the BBC's commissioning editor for history, said: "This documentary is an extraordinary glimpse into a deeply personal side of the royal family that is rarely seen."
Four days of events to celebrate the Platinum Jubilee begin on June 2 with the annual Trooping the Colour military parade in central London followed by a thanksgiving service at St Paul's Cathedral, a concert outside Buckingham Palace, and a pageant through the British capital on subsequent days.
The Queen's 70 years on the throne will also be marked with events across the Commonwealth.Â
In Australia this will include the lighting of a Platinum Jubilee Beacon in Canberra, while buildings and monuments around the nation will be illuminated in royal purple.
