Why did the Spice Girls not perform at the closing ceremony of the 2012 London Olympics?

I'm sure many of you remember that the Spice Girls did do actually show up and perform at the closing ceremony, but I also remember the first that news got out that the Olympics were coming to London they said that they wanted the Spice Girls to perform at the closing ceremony. I know that it had been years since the Spice Girls had last performed together, so they obviously need to practice, but I imagine the Girls Spice would have to have been contact with the Organisers somewhere in those years, and I don't think it would have been a massive shock if they had decided to not perform and that Victoria Beckham didn't want to.<br><br>So what was it that made the Spice Girls decide to perform?