Doug Allan

Cousteau helps himself to a folder of maps and takes them to a desk beneath a green shaded lamp.

From his dispatched case, he produces his precious Leica camera.

He pauses, listening to a murmur of voices in the corridor beyond the door.

But the sound soon fades, and he gets to work photographing the documents, capturing enemy intelligence, gun emplacements, and stockpiles of ammunition.

Suddenly he hears footsteps approaching, and a shadow crosses the frosted glass.

There is a loud exchange in Italian just outside the door, and Cousteau has just enough time to slide the camera back into his case before the handle is rattled.

But it stills as swiftly as it started, and whoever it is moves on.

Cousteau swallows hard.

His luck might not hold.

It is time to go.

Fastening his dispatch case with the Leica safe inside, he returns the folder to its place, then exits the room, shuts the door, and leaves the building.

Even an intrepid explorer like him recognizes risk when he sees it, and he's in no doubt about the consequences of mistakes on a mission like this.

He has just survived, arguably, the most dangerous ten minutes of his life.

After the war, Cousteau is awarded the Légion d'honneur, France's highest order of merit, in recognition of his courageous service to the resistance.

But before the conflict is over, Simone has a brainwave.

She asks her father if he knows anyone at Air Liquide who might be able to help her husband in his mission to breathe underwater.

So it is that Cousteau meets a quiet engineer by the name of Emile Gagnin.

He shows Cousteau a small device called a demand regulator, which is designed to release compressed gas only when required.

Intrigued, Cousteau immediately sees how such a mechanism might be adapted for diving, and the pair begin adapting the regulator for underwater use.

But their first attempt, in January 1943, works only when Cousteau is horizontal.