In early 2003, GCHQ analyst Katharine Gun obtains a memo detailing a joint United States and British operation to spy on diplomats from several non–permanent United Nations Security Council member states to "dig dirt" on them. This was to influence the Security Council into passing a resolution supporting an invasion of Iraq.

Angered that the UK is being led into a war on false pretences, Katharine leaks the memo. It makes its way to The Observer journalist 

Martin Bright.

The leaked memo's publication in March 2003 generates public and media interest. The Drudge Report attempts to discredit the document as a fake, as staffer Nicole Mowbray had inadvertently changed the text from American to British English with a spellchecker. However, Martin is able to produce the original memo, confirming its authenticity.

Katharine's actions prompt GCHQ to launch an internal investigation. Katharine confesses to leaking the memo. She is arrested and detained, before being released on bail. The British Government decides to charge her with violating the Official Secrets Act.