The raid on Germany's dams gets off to a rocky start as the crews struggle to clear the airfield in their planes loaded with four tonne bouncing bombs. Of the 133 young men who flew on the raid, only 80 survive.

Wallis tries to get his revolutionary bomb to work, which will require the invention of a new aiming device. Dan Snow takes to the skies to test it, but accuracy isn't the only problem.

24-year-old wing commander Guy Gibson has less than eight weeks to recruit and train 147 aircrew for a top-secret mission that will require them to learn to fly at super low attitudes at night towards targets on water.