It was much more than just a one night stand.
Mel B had previously admitted her tryst with Geri but now it appears that it was much more than that.
Mel B recently confessed to Piers Morgan on a live show ahead of their new $15 million tour that the two women enjoyed a steamy tryst.
However it turned out to be more.
One source revealed: "They were two women who knew what they wanted.
It was very much a case of those two against the world."
And it appears that Mel, 43, who joked that Geri, 46, was heartbroken when their secret relationship ended as the all female band became famous around the world.
The two women – known during their 1990s pop heyday as 'Scary and Ginger' – are looking forward to their new 13 date tour.
The pair has remained friends but at one time they were heavily involved with one another.
Friends who knew them back then have revealed their relationship lasted at least a year.
One recalls: "It was in the very early days of the Spice Girls and their relationship lasted far longer than one night – it was at least 12 months."
The source says their relationship was 'lust at first sight' when the two met for the first time in 1994 after being chosen to join another girl band, then known as 'Touch.
Mel and Geri, then aged 18 and 21 respectively, instantly fell for one another on and off stage.
They confided their deepest secrets and also regularly shared a bed according to friends they were 'absolutely inseparable' at the time.
The source adds: "They were so close - they were together in every sense of the word.
"They were brought together through the circumstances of being in the band but their living arrangements in Maidenhead meant that they had lots of time alone."
Geri – who is now married to Christian Horner and has two children – has enjoyed several affairs with women and both she and Mel experimented with both sexes when they were together.
However, it was Mel and Geri, who shared a special bond.
"Geri's father had not long passed away and she was hurting from that, while Mel was a long way from home. While things were very exciting for them, it was also daunting," adds the source.
"They were one another's support, they got one another and were actually very similar.
"They were the stand-out best friends in the band. They loved one another like sisters – but also fell out in the way siblings do."
During the recent interview with Piers Morgan he asked about their tryst.
Mel replied: 'Oh, stop it, you pervert.' She then insisted it had happened only once.
However, it now appears the two women enjoyed a much bigger affair during those early days.
Mother–of–three Mel B is currently single after divorcing film producer Stephen Belafonte in 2017, while Horner Geri is happily married.
And it is understood she did not want to embarrass her former lover before the new tour.
"She didn't want to put too much on the record that would have embarrassed Geri," says the source.
"The view is very much that Geri wants to zip up the past. Her life is now all about cooking and country estates, and Mel likes to remind her of her younger years at times but she actually wouldn't want to invade her privacy completely."