She nods dutifully and steps forward. It’s not just the fear of getting it wrong. There’s something in the intensity of his gaze that unnerves her. He seems to love watching her, scrutinising her every syllable and hand gesture, and his delight never wavers, even when she makes a mistake. If anything, he seems to enjoy correcting her: lifting her arm to improve a gesture or standing behind her and putting his hands on her stomach and pulling tightly, making her draw up the energy from her feet. She’s grateful that he’s so patient with her – not like her sisters, who get cross when she’s slow to learn a new conjuring.

They’ve spent all week on a new spell and she’s been practising hard to get it right. She adopts the stance, raising her arms and chanting quietly as the energy flows up through her feet and legs and into her arms. She speaks the words he’s taught her, ‘Papilionem ostenderem,’ and a butterfly appears above her head. It beats its delicate blue wings and dances on the air. She continues to chant and another pops into existence, and then another.

She wants to smile, but her head hurts from having to focus. She’s been able to shift into animal shape since she was small, but bringing a new living creature into existence is far more difficult, and the butterfly is so fragile. Her concentration wanders and one of the creatures stops fluttering its wings and drops to the ground. She steals a glance at Merlin, who is watching her intently.

‘Papilionem ostenderem,’ she says again, only this time she stumbles over the words. A pitiful creature appears in the air, one of its wings twice the size of the other and its antennae missing. It flaps uselessly and drops to her feet with a sad little thud. She tries again and dozens more appear, but their colours are dull, their wings misshapen and tattered.

Angry at herself, she lowers her arms and the insects drop around her feet. All week she’s been creating perfect butterflies, but she gets so nervous in front of him. It’s obvious she made a mess of the spell, so why isn’t he correcting her? Her sisters would be chiding her by now, but he appears delighted.

‘Magnificent!’ he cries, clapping his hands.

She tries to return his smile but all she can think about are the poor creatures on the ground, their bodies littering the glass floor in a squirming carpet. He strides over to her and the sound of insect wings being crushed makes her wince. She wishes she could put them out of their misery, but she doesn’t know how to magic them out of existence. ‘Can you help them?’ she asks.

Merlin looks down his nose at the dying creatures. ‘Did you know that in the earthly realm boys would fasten threads of flax to the bodies of butterflies and fly them like tiny living kites?’ He tells her this as if it should amuse her. She gulps and shakes her head.