Benny, Björn and Frida drop in for first anniversary of London’s Abba Voyage

On stage, digital technology gave the 3,000-strong audience at the Abba arena in east London perfectly recreated youthful versions of Agnetha, Benny, Björn and Anni-Frid.

At the rear of the purpose-built auditorium, three of the legendary group, now in their 70s, appeared in real life, waving like the pop royalty they are. The crowd was in ecstatic meltdown.

Benny Anderson, Björn Ulvaeus and Anni-Frid (Frida) Lyngstad were at the arena on Saturday evening to celebrate the first anniversary of the phenomenally successful show, Abba Voyage, featuring avatar versions of the band members.

More than 1.3m tickets have been sold to date, and the show has been extended to run at its London venue until May 2024. There are reports of a world tour, and Ulvaeus has suggested that replicas of the purpose-built arena could be constructed in Asia, Australia and North America.

For Kim Smith, who had travelled from Portsmouth to see the show with her daughter Lucy as a 62nd birthday treat, it was an emotional experience. “It took me back 40 years,” she said. “I was so overwhelmed that I cried.”

Abba Voyage opened a year ago to five-star reviews. “The effect is genuinely jaw-dropping … it’s almost impossible to tell you’re not watching human beings,” the Guardian’s Alexis Petridis wrote. Others described it as incredible, spectacular, dazzling and epic.

It took seven years and $175m to develop the technology and build the arena near the Queen Elizabeth Olympic Park in Stratford, east London. The four members of the band spent a month in motion-capture suits and helmets to help create the avatars – or Abbatars – that now “perform” seven times a week while their human counterparts can put their feet up.

“It was meticulously prepared, enormously expensive and incredibly difficult to create believable digital people,” said Svana Gisla, a producer of Abba Voyage. “But the result is magical.”

The avatars created by the visual effects masters Industrial Light & Magic had to “blend with the physical world”, including a 10-piece live band, said Gisla. “The join needed to be invisible. It needed to become one unit.

“Technology is the vehicle, but the audience shouldn’t feel the technology. We only got into the arena six weeks before the show opened, and at that point we couldn’t be sure it was going to work.”

The 90-minute show is the same for every performance, unlike a live gig where artists can mix up the numbers they perform or tailor their chats to the audience. But, said Gisla, the live band – which has its own spotlight mid-show – and the audience make each show unique.

The fans come in wigs, sequins and shiny catsuits, some as old or older than Abba, others born long after the band’s last live performance in 1982. The 350 shows since the opening on 27 May last year have attracted people from more than 140 countries.

Brendan Wagner and Steven Aney had come from Brisbane and Melbourne respectively to meet up with old friends Sophie Doherty and Jen Woods for Saturday’s matinee. They described it as “amazing, fantastic” with even the textures of the avatar’s spectacular costumes “completely believable”.

Up to 200 staff – 75% recruited in the local area – work on each performance, including those whose role includes enforcing the ban on photographs and video.

“It’s lovely when people put their phones in their pockets and are there in the moment. It’s very rare to be at a concert where people are just dancing and singing, and not spending 80% of their time filming other people,” said Gisla.

Last week, Abba ruled out a reunion for next year’s Eurovision in Stockholm, which will be 50 years after the band’s performance of Waterloo won the competition. They have previously reportedly turned down the offer of $1bn to reunite. “We can celebrate 50 years of Abba without us being on stage,” Ulvaeus told the BBC.

Neither can their avatars perform outside the bespoke arena. “We joke that they don’t do special appearances, award ceremonies or barmitzvahs, because they can’t,” said Gisla.

Other performers and promoters have watched the pioneering show’s extraordinary success, with some inevitably pondering their own futures on stage.

Related: ‘It’s a no’: Abba rule out appearing at 50th anniversary of Eurovision win

“Good luck to them,” said Gisla. “It’s very expensive at the moment, and technology moves very quickly, especially AI driven technology, which is probably further along than we even imagine. But the technology isn’t enough. There is also an emotional experience in the arena.”

Ludvig Anderssen, another producer on the show, attributed that to the blurring of “the borderline between real and fantasy worlds. It triggers feelings about youth, ageing, mortality and immortality”.

Avatars would not replace live performance, Gisla said. “Musicians need to perform and audiences want to see performances, that’s never going to die. That’s an art form that has been alive for thousands of years. That’s the human connection that we need in life, and this is just another form of entertainment.”