Time and after time, one British company outsmarted the Germans in Crete. If the Nazis planned a sneak-raid and began it five miles away, the British knew at once – and were ready for them. If a Stuka dive-bombing attack was decided on, they got into hiding an hour before it began. They knew exactly when to counter-attack too.

How was it done? If anyone had told the Germans, they just wouldn’t have believed it. The secret lay in a strange invisible link between Private Bill Roberts and his twin brother, Jack…