The Hogwarts ties, gowns and familiar smiles told their own story as a generation who cut its teeth on the first Harry Potter book nearly 20 years ago turned out on Tuesday night to see the latest chapter in their hero’s story.

The first fans to witness the theatrical adaption of the boy wizard’s tale emerged blinking, beaming and giving the thumbs up, following a preview on Tuesday evening of Harry Potter and the Cursed Child.

“I was expecting the tears and the laughter. I wasn’t expecting the goose pimples,” said Rosa Hadjiska, 23, who spoke of growing up with JK Rowling’s bestselling series of novels.

“It was amazing, and a shock. It’s unbelievable and I can’t wait for the next part.”

Like Cor, others emerging from the production at the Palace Theatre in London’s West End were generous in their praise for what has already been widely tipped as a likely box office sensation, after breaking records by selling 175,000 tickets in 24 hours.

“It blew my expectations out of the water,” said Susanna Piny, a graduate student who had travelled from Rhode Island and was among a fair number of audience members who arrived decked out in the tie and gown worn by students of the Hogwarts school attended by Potter and his friends.

“We bought our tickets as soon as they came out. I think that I was something like twelve hundredth in line,” said the 28-year-old, who was visiting with her mother, Melanie.

Set 19 years after the end of author JK Rowling’s last Potter novel, the two-part play continues the story of Harry Potter, who is now working at the Ministry of Magic while his son Albus negotiates his way through Hogwarts.

Before the performance Shama Hussain, a 27-year-old studying in the UK, who confessed to being obsessed with all things Potter from an early age, was waiting patiently in line. “I feel like being here for this was almost the whole point of moving to London,” said the New Yorker, who signed up for preview tickets last year.

“I am just really excited what the new format is. It’s going to be great to see it. [Rowling] says this is the platform for it and I have full trust in her.”

Like others, she feared that Rowling’s plea for fans not to broadcast the secret of the story would be in vain. “I think it will be hard. It’s going to be on the internet. But you know … fingers crossed people keep it to themselves.”

It wasn’t all joy though. Among the disappointed was Grace Palaganas, who had travelled from the Philippines with her daughter for a six-day holiday in the UK, the highlight of which they hoped would be the play.

“We queued up for more than an hour to get tickets but there are none. We will be coming back in July but we don’t know if there are tickets. I guess we will will try our luck again,” she said.

The two-part production will open at the Palace Theatre at the end of July.

Last week audiences for previews were asked to arrive an hour early and have their bags searched. The request follows controversy surrounding Benedict Cumberbatch’s Hamlet at the Barbican, when security staff struggled to prevent audience members from filming or photographing, forcing the star to urge fans not to record his performance.

• This article was amended on 8 June 2016 to correct the name of Rosa Hadjiska.