An insider told the paper: "The girls have known all along that this would be the last time they would all work together.
"At the press conference to announce the tour, they deliberately dodged questions about future plans because they did not want to spoil the excitement."
The girlband - who are currently celebrating ten years together - are thought to be keen to move on now that they're heading into their 30s.
And despite Nadine's hope that Girls Aloud would never split, the source claims: "They all felt it wasn't right for them to be singing songs like Love Machine and performing the same way when they're in the their thirties.
"They all want to make this a way to bow out on a high and walk away for the next chapter in their lives without constant questions about when they will be getting back together."