"Viva Forever!" was the brainchild of producer Judy Craymer, whose "Mamma Mia!" musical based on the hits of ABBA has earned nearly $2 billion worldwide and spawned a hit movie starring Meryl Streep.
She teamed up with British comedian Jennifer Saunders to create a story about the central character Viva, a sprightly teenager who, along with her friends, gets into the final stages of a TV singing contest closely resembling "The X Factor".
To boost flagging audience figures - a nod to "The X Factor"s real-life ratings woes in Britain this season - their "mentor" springs a surprise and throws out three members of the band to leave Viva on her own.
What follows is part morality tale examining what is more important - friends, family or fame - and part satire on reality television, including a callous, Simon Cowell-like producer.
"We love you Judy!" said Geri Halliwell at the end of the show, which closed with a romp through some of the Spice Girls' biggest hits including "Spice Up Your Life".
"Thank you for making the Spice Girls' dream come true," Halliwell added.
Halliwell was joined on stage by Victoria Beckham, Melanie Brown, Emma Bunton and Melanie Chisholm, who together stormed the charts in the 1990s and put "girl power" on the map.
Beckham, who arrived at the London premiere after her ex-bandmates, sat with her soccer star husband David and three sons, who clapped along to the music during the final medley.
Now all young mothers in their late 30s and early 40s, The Spice Girls are still affectionately known by the nicknames they adopted in the band - Posh (Beckham), Scary (Brown), Baby (Bunton), Sporty (Chisholm) and Ginger (Halliwell).
They were hailed as modern-day feminists by some and dismissed as vacuous pop princesses by others, but their success is beyond doubt. They sold 55 million records, had nine British No. 1 singles and three back-to-back Christmas No. 1s.
The band broke up around 12 years ago, and internal bickering among the members was long the delight of Britain's celebrity-obsessed tabloids.
Perhaps surprisingly, given the bust-ups and hissy fits, the group has been united in its backing of the new musical, and underlining the Spice Girls' lasting popularity they played a major part in the closing ceremony at the London Olympics.
Paul Taylor, writing in the Independent newspaper, gave the musical two stars out of five in his review.
"The Spice Girls' songs, with their clever hooks and catchy rhythms, are better at projecting an attitude than fleshing out a dramatic situation," he wrote, describing Saunders' story as "charmless", "messy" and "lackluster".
"Not only does her script rarely give you that necessary gleeful sense of expectancy about where the songs are going to be shoe-horned in, but it's embarrassingly derivative of 'Mamma Mia!' and looks way past its sell-by date in its utterly surprise-free satiric swipe at 'X Factor'."
Saunders said before the show that she considered herself the "sixth" Spice Girl.
"We used to travel around everywhere to see them and they were so great with my kids," said the 54-year-old, best known for playing a self-absorbed, eccentric mother in the popular British comedy series "Absolutely Fabulous".
"The thought of a Spice Girls musical written by somebody else was not acceptable," she told the Daily Mirror newspaper. "Because I was so close to them, I couldn't let it slip through my fingers."
(Reporting by Mike Collett-White, editing by Jill Serjeant)