In this Untold Story we look at Identification Friend or Foe Mk II (IFF Mk II) which was a radio transponder fitted to RAF aircraft in 1940. It returned a unique radar signal to Britain’s Chain Home stations, distinguishing friendly planes from enemy aircraft during the Battle of Britain.

Untold Stories is a series of short films, narrated by our own experts, that uncover the remarkable lesser-known stories of the Battle of Britain while spotlighting the people, tactics, and technology brought to life through the RAF Museum’s collection.

Look out for our final episode, episode 12 coming soon.