Music
Halliwell was talking on GMTV about reuniting with the girl power pop group when she let the title slip.
The popstar claimed the song was "absolutely amazing", commenting: "Emma and I initially worked on it with the original writers we used to collaborate with and then the other girls chipped in later on, adding lyrics.
"It's a Spice Girl classic. We are so proud of it. We started putting words down before we even had the finalised yes from everyone.
She added: "It was kind of like a prayer - when you kind of put the footwork in hoping that it will happen - so it is a really special song, it's kind of magical...It's a big love song."
The Spice Girls Greatest Hits album is released on November 12, with the single rumoured to be released one week later.
More: Music, Spice Girls Reunited
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