Charles, who was intimately involved with the entire project, even persuaded his mother to sit down with him, Gogglebox-style, to watch some of the clips and reminisce about their times together.

Other members of the Royal Family — including her grandchildren Princes William and Harry — are also similarly shown discussing the footage, much of which had never been seen before, even by them.

Indeed, shoot-from-the-cuff Harry provides possibly one of the best lines from the entire documentary when he exclaims on seeing his grandfather, Prince Philip, playing with a young Charles: ‘Look how good-looking Grandpa is there! He’s an absolute stud! Those glasses, slicked-back hair . . . presumably he was in the Navy then?’

The film was shot by the Queen, Prince Philip or, on occasions, Princess Margaret. ‘The whole collection provides a wonderful insight into my Mama’s long life,’ says Charles.

The royal chauffeur: As a future king, Charles had not one but two pedal cars to play with. Watching on is Princess Anne

The footage shows a young Prince Charles crashing one car into a wall, much to the hilarity of his sons, when they view it

Off his trolley: Prince Philip joins his children racing down the hill at Balmoral . . . and almost flashes more than just his underwear when he falls off

‘That was nearly very embarrassing for Grandpa!’ says the watching William. ‘Grandpa is having more fun than anyone else. There is something about banks that all children just want to roll down. George is just the same’