Just what is the big fuss about Heathers? It’s a school-of-Legally-Blonde musical derived from a cult movie which had an enthusiastic six-week run at The Other Palace, mostly for existing fans of the Winona Ryder 1988 film, and its producers have gambled on a three month transfer to the Theatre Royal Haymarket.

But it has both bloggers and print critics in ferment. The press weren’t allowed in to the initial June-to-August run on the grounds it was ‘a preview’, which didn’t stop the noble Lord Lloyd Webber from charging £60 a ticket despite the cardboard sets and starless casting. Although Carrie Hope Fletcher, giving a strong and spirited performance as the central figure Veronica, has an enormous online following among young women both for her acting, her vlogging and now three well-regarded novels based on her own life experience.

Without any approved formal reviews, producers released a lot of marketing based on vox pop endorsements and quoting tweets from the fan base rather than star ratings from the Telegraph or the Standard. The show sold out. This is becoming big business – at low or no cost, it’s possible to put together a cluster of ‘TripAdvisor’ type recommendations for any show, and it’s a useful insurance in case professional critics savage it.

New musicals, particularly those that are aimed at the growing under-30s market for pop and rock scored entertainments – Knights of the Rose, Thriller Live, Eugenius!, Mean Girls, Dreamgirls – is there one called ‘Scream, Girls’? because if not there will be soon – host generously-catered promotional events for the bloggers which effectively buy them almost-free advertising.

Nor is it always considered essential to use a PR company. Younger producers, like Heathers’ Paul Taylor-Mills are exploring new directions. Katy Lipson of Aria Entertainments, who produced the successful Addams Family Musical tour featuring Hope Fletcher as Wednesday, recently sent a shout-out on social media for bloggers and fringe critics to register directly with her for invitations to productions. She says it’s to keep options open, but it may be the new way forward.

On transfer, the show is having press nights – about four of them, most performances boosted by enthusiasts who were given free or £5 tickets through the Haymarket’s outreach scheme for 16-30 year olds Masterclass, which pretty much guaranteed plenty of hand-jiving to the tunes and standing ovations.

Whether or not the musical itself is a success at the Haymarket, the marketing deserves five stars. There’s a world of difference between selling out a 300-seater during the school holidays to an enthusiastic Winona-Ryder-loving audience, and filling a big West End house on wet Tuesdays in November.

But as Heather Duke says in the movie: “Some people need different kinds of convincing than others.”