The new book Harry Potter and the Cursed Child: The Journey tells you all you’d want to know about how the play came to be. Here’s five things we learned reading it, and one you might have known already.

Gillyweed?

Sam Clemmett and Anthony Boyle, who played Albus and Scorpius in the original London production, had to take an unusual taste test. In the play they have to eat Gillyweed, the plant that when consumed has the effect of generating webbing between the fingers and toes, as well as gills to breathe underwater. To stand in for Gillyweed, they were offered a range of edible possibilities including actual seaweed and samphire. They settled on apple skin!

The owls that are unseen

A whole flock of owls were created for the Hogwarts owlery in the play. These were meticulously created from many fabrics, feathers, sturdy brown paper and leather. But because they are nested in the upper reaches of the stage, the audience can’t even see them! ‘We knew that nobody would ever see them,’ props supervisor Lisa Buckley explains in the book, ‘but it was such a lovely thing to create this flock of owls. Sometimes, it’s actually nice to provide props that nobody really sees, but you know are there.’

We can work it out

Movement director Steven Hoggett liked to put the original London production cast through their paces, ensuring they were physically fit for what he calls a ‘ballistic’ performance every night. Each day of the week had a different physical workout to contend with (from circuit training to silly dances on ‘Fun Friday’), but the week would always start and end with yoga: ‘to centre everyone again.’

Muggles allowed

Unbelievably, lighting designer Neil Austin had never read the Harry Potter stories, or seen any of the films. As such, he was designated the team Muggle in the original London production cast and crew. That way he ensured that the production was accessible to all audience members. ‘I think it was quite helpful to have someone who doesn’t know the canon,’ says Austin in The Journey. ‘You can forget that this show needs to appeal not only to the fans, to the people who love the books, but also to the grandparents who haven’t read them and are taking the kids to the show for a treat. Or even the standard theatregoer, who’s heard this is a good show, but isn’t a Harry Potter fan, and is wondering if it’s got anything in it for them.’ We’ll let him off then...

DO drop your t’s!

During rehearsals for the original London production, the cast and crew instituted a House Cup and everyone got themselves sorted. They had a scoreboard and a winning house every week, with points being awarded, but also deducted. For example, five points were taken for mispronouncing Voldemort with a hard t. Harry Potter and the Cursed Child uses J.K. Rowling’s original intention for the pronunciation, ending with a soft, French-sounding Vold-de-mor.

One other thing we learnt (which may not surprise some) is how boisterous the New York audiences turned out to be compared to London. ‘The weirdest thing was that they clap upon people’s entrances here, which doesn’t happen in the UK as much,’ says Paul Thornley, who played Ron in London and on Broadway. ‘And some comment more. But if people are involved in something, I don’t have a problem with that. I quite like it.’ And so do we!

Harry Potter and the Cursed Child: The Journey is available now in the US and UK in print and digital.