Just hours after being told of her father's sudden death, the then-Princess Elizabeth boarded a plane back to London to start her new role as Queen.

Before she left she asked for an hour alone to come to terms with the heartbreaking loss of her dad, before committing herself to her public duty and discussing the practicalities of her return home.

As they sat on the plane home on February 6, 1952, Prince Philip took an intimate video of his wife, which shows her looking deep in thought and emotional.

The 25-second clip shows her eating lunch with Lady in Waiting Pamela Mountbatten and three male aides at the start of the BOAC flight from Entebbe, Uganda to London.

The photo shows the Queen looking deep in thought

When she realises she is being filmed by her husband, she breaks into a warm, brave smile - an early sign of the inner strength and resolve to put duty first she has shown many, many times since.

A few moments later she looks more emotional - her sad expression a reminder that this is a young woman who has just lost her father and at the same time inherited the huge responsibility for the Crown.

Aged just 25, she was now Sovereign of 32 countries, ruling over an estimated 200 million people worldwide, who were now looking to her to lead the way.

This unprecedented glimpse into one of the most intimate moments of royal life had not even been seen by Prince Charles until it was unearthed for his televised tribute to his mother, shown on BBC1 in 2012.

When the enormity of the moment he was witnessing on screen dawned on him he said in shock: "Oh... "That must be on the aeroplane.

The Princess and Philip were just days into their trip

"I presume it's my father taking the photograph. I've never seen this before.

"So these must have been the first pictures taken of my mama after she knew she was Queen."

Charles looked emotional as he contemplated the huge constitutional responsibility that had fallen on his mother in a moment of such personal sadness.

He appeared to be choking back tears as watched his mother - dressed in a simple navy blue suit that she later swapped for black clothes on arrival in London - contemplate her destiny.

The King died suddenly in his sleep

He said: "One of my greatest regrets is not having known him (his grandfather King George VI) - and I really mind that."

As soon as news reached them of King George's death the new Queen and Philip hastily flew home from Africa - just six days into their trip - to Charles and Anne, who were then just three and one.

On the night he passed away in his bed at Sandringham they had been in the Treetops hotel in Kenya, and had enjoyed filming the wild animals running beneath them the day before.

"I think my mother must have probably inherited the interest in film from her father...my mama kept up the habit.

"Both my parents seemed to enjoy filming things."