‘Lilibet, you’re going to be Queen of England one day. You are not “lots of people”.’ Exasperated, Margaret stalks across the stage, her heels clacking on the wooden boards.

‘Margaret!’ There is a hiss from the back of the stage where Crawfie, their governess, is beckoning. ‘You too, Lilibet. The King and Queen are just coming in now. You need to take your places for the show.’

Elizabeth draws a breath. It doesn’t matter that Philip isn’t here. She will not be disappointed. He is coming for Christmas. She will see him soon.

Beyond the curtains she can hear the rumble and scrape of chairs being pushed back as the audience stands for her parents.

‘Quick, into the basket!’ Cyril Woods scampers across the stage. Elizabeth likes him. He is jaunty and bright-eyed, and he dances and sings nearly as well as Margaret. The two of them carry her scenes, Elizabeth knows. She learns her lines and moves when she is supposed to, but she doesn’t have Margaret’s dazzle. Next to her sister, she is muted, dull. That is how she feels, anyway.

But she is the elder; she will be Queen. So she has the starring role. It is Elizabeth who is playing Aladdin, in a shockingly short jacket and tights that make her feel very exposed. Margaret is Princess Roxana, which she doesn’t mind as she gets to wear a gorgeously embroidered silk robe and a tiara.

For the opening scene, they are to jump out of a huge laundry basket. The back has been cut out so they can crouch behind it. There isn’t much room and Cyril keeps touching her leg by accident. ‘Sorry,’ he mutters. ‘Sorry.’

Elizabeth’s heart is thudding. Oh, how she hates this moment before the curtain goes up! Her mind has gone blank. Her costume is too tight and she can’t remember a single line. The wicker basket is tickling her cheek and her legs are already stiffening. As the Guards’ orchestra strikes up the fanfare, she is gripped by the longing to leap up and bolt from the stage, to run out into the Upper Ward and down to the stables. To ride far, ride fast, to a place where there is no one to fail and no one to please and no duty to be done.

But she cannot do that. The show is one of the few contributions she can make to the war effort. Proceeds will go to the Royal Household Knitting Wool Fund to provide comforts for the troops who are fighting for their country, Elizabeth reminds herself sternly. They aren’t allowed to run away. All that is being asked of her is to sing and dance. What kind of example would she set if she were to refuse even that?

It is too late now in any case. The orchestra is reaching a crescendo, the drums are rolling and there is a swishing of velvet and a creaking of ropes as the curtains are hauled back.