For over 100 years, MI5 has been a secret service. Working in the shadows, its officers and agents kept Britain safe. Now, the world is at war with global terrorism and we are all on the frontline. MI5 is what stands between us and the horrors of terrorism. But rumor and intrigue surrounded secret operations, until now. MI5 has opened its files and we can discover more about the allegations that have surrounded this secret service for decades.