On May 26th the "Tunny Gallery" opened at the National Museum of Computing at Bletchley Park. This cover was issued to celebrate the event.
The doublesided design by Andy Partridge commemorates the secret work undertaken during WW2 to crack a new binary code used by German High Command for its most secret messages. In conjunction with Colossus the invention of "The Tunny Machine" heralded the modern computer age.
A rebuilt Tunny Machine when on display at an event attended by veterans who originally worked it.