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The Spice Girls gave fans what they want -- what they really, really want -- Tuesday, reuniting onstage to announce the details of a musical based on their songs.

Producers stress that the stage show "Viva Forever" isn't a biography of the band, but there are plenty of real-life resonances for the 1990s "Girl Power" group in its tale of female empowerment and friendship tested by fame. The show opens in London in December.

"We're going to be introducing a whole new generation to `Girl Power,"' said Victoria "Posh Spice" Beckham, who attended a media launch alongside Emma Bunton, Geri Halliwell, Melanie Chisholm and Melanie Brown -- also known as Baby, Ginger, Sporty and Scary Spice.

"Viva Forever" aims to tap the same vast female fan base as "Mamma Mia," which has been produced in 14 languages around the world and spawned a hit film starring Meryl Streep. The Spice Girls show tells the story of four friends whose bond becomes strained when their band enters a TV talent show.

Scored to Spice Girls hits including "Wannabe," "Spice Up Your Life," "Mama" and the title track, it was written by comedian Jennifer Saunders -- co-creator of celebrity-skewering sitcom "Absolutely Fabulous" -- and produced by Judy Craymer, the woman behind world-conquering ABBA musical "Mamma Mia."

Focusing on female friends and mother-daughter relationships, Craymer called the musical "a heartwarming family tale" that touches on the role of media and celebrity in the modern world.

"There's just something empowering about women's stories that interests me a lot," Craymer said.

Saunders -- who once spoofed the Spice Girls in a mock band called the Sugar Lumps -- said the show aimed to catch "the joy that they brought, their energy and their positivity."

The Spice Girls said they were delighted with the show, which was unveiled for the press in the grand neo-Gothic hotel where the video for their 1996 breakthrough hit "Wannabe" -- in which the band promised to "tell you what I want, what I really, really want" -- was filmed.

"Sixteen years ago when we were writing the words `zig-a-zig-ah,' we could never have imagined they would be in a West End show," Halliwell said, quoting the catchy if confusing refrain of "Wannabe."

Added Chisholm: "It's better than we could ever have imagined."

"They sing it better than us," said Brown.

The band's outsized personalities and Halliwell's Union Jack dress made them icons of 1990s "Cool Britannia," and they sold 75 million records around the world. Halliwell left the group acrimoniously in 1998 and the Spice Girls effectively split a decade ago.

The five members have not appeared together since a 2007-2008 reunion tour.

Since then, several have released solo records, and Beckham has become a fashion designer and part of a celebrity power couple with her soccer-star husband, David Beckham.

Despite their past differences, they appeared in good spirits as they joked and praised one another Tuesday.

Halliwell said her band mates "individually and collectively, they're really lovely."

"She's only saying that because she left!" said Chisholm.

True, Halliwell conceded, "but they took me back."

"Viva Forever" begins previews Nov. 27 and opens Dec. 11 at London's Piccadilly Theatre.