Even in previews, as the cast finds its footing and the creative team makes adjustments, the show is setting box-office records. Potter fans have been filling up the Lyric, one of Broadway's largest theatres, and the $2.1 million the play took in during the first week of April was more than any play had previously grossed in a single week.

The record-setting $35.5 million capitalisation – the amount raised from producers and investors to pay an unusually large cast and crew, rehearse an unusually long show and build an unusually elaborate production – was disclosed in a filing with the Securities and Exchange Commission. By comparison, most non-musical plays on Broadway are between $3 million and $5 million, and even the splashiest musicals rarely top more than $25 million.

But the capitalisation is only a portion of what it took to pave the way for Cursed Child to get to Broadway.

The Ambassador Theatre Group, the British theatre giant that operates the Lyric, spent about $23 million to persuade its previous occupant, Cirque du Soleil, to shutter its Paramour musical and make way for Cursed Child, according to two people with knowledge of the transaction.

The play, a two-part experience with a running time of more than five hours, is a sequel to the series of young adult fantasy novels written by J.K. Rowling about a boy wizard. Cursed Child takes place 19 years after the final book, at a time when Harry and his friends have become parents.

Cursed Child was written by Jack Thorne, based on a story by Thorne, Rowling and director John Tiffany. It was developed in Britain and has been sold out in London's West End for 22 months, and last year it won a record nine Olivier awards including one for best play.