In 2008, she was called by her friend James Curtis, deputy head of Mildfields School, after Harold Saxon gave a Commemoration Speech at the school. Curtis voiced his concerns about Saxon and his supposed background at Mildfields. Rook did some background research but didn't find anything. When she called Curtis back, he told her he had been having a "senior moment" and now perfectly remembered Saxon's time at the school. Vivien noticed he sounded off in his response, particularly after he ended with a remark about "Who could forget Harry Saxon?" (PROSE: Speech Day)
Her second interview with Harriet Jones came after Saxon's election. While it was mostly about Jones' return to prominence as a local hospital campaigner, the former PM said that Saxon's background didn't add up. (PROSE: Judge, Jury, and Executioner)
After doing more research, Rook turned up at 10 Downing Street claiming to be seeking an interview with Lucy Saxon. She told Lucy the truth about Saxon, explaining that he had only been in existence since Harriet Jones' downfall. However, Saxon had already told Lucy about his true identity and intentions, and Saxon himself came in and ordered four Toclafane to kill Rook.
However, Rook had prepared a contingency plan, and when she didn't return to her desk by 10pm, an email was automatically sent to Torchwood. It was retrieved by Jack Harkness, the Tenth Doctor, and Martha Jones on Martha's laptop. Vivien had attached the Saxon files, including the Archangel document, which allowed the three to find out how Saxon had mind-controlled most of the world and use it against Saxon. (TV: The Sound of Drums)