The gang of three hurried down a set of steep stone steps cut into the cliff that led on to the beach.

CLINK! CLANK! CLUNK!

For now, they couldn’t hear anyone following them.

The beach was deserted, as well it might be on a dark, stormy winter night such as this.

“I think we lost them!” said Eric, breathless from running.

The boy looked across the rolling waves out to sea. A deep sense of dread crashed over him as he spotted something slowly rise from the water.

At first it was just a long, thin tube. A periscope!

Then a flag. The swastika!

Then the metal hull of a submarine reared out of the sea.

“You were right, Eric,” muttered a shocked Sid. “It’s a Nazi U-boat!”

In times like this, when you are faced with grave danger, there is always one simple option.

RUN AWAY!

RUN AWAY! AS FAST AS YOU CAN!

RUN RUN RUN RUN RUN FASTER FASTER FASTER!

“Let’s get out of here!” exclaimed Eric. “FAST!”

“Help me up, lad!” said Sid. “These tin legs of mine have got creaky.”

As Eric and Gertrude hauled the old man to his feet, behind them they heard the crunch of feet on the pebbles.

It was the twins, their machine guns pointing right at them.

“Put your hands in the air!” ordered Bertha.

“One move and we will shoot!” commanded Helene.

Eric and Sid shared a look.

“Are we still allowed to put our hands up, though?” asked Sid.

“What?” barked Bertha.

“Does that count as moving?”

“Yes!” snapped Bertha. “Put your hands in the air. One move after that and we will shoot!”

“It could have been clearer!” muttered Sid.

“Don’t push your luck, old-timer, or you will find yourself floating face down in the sea with a hail of bullets in your back,” replied Bertha.

It was a chilling image, and silenced Sid and Eric in an instant.

“We are going to keep you alive. For now. Until we find out exactly what you know and crucially who you’ve told about our little plan,” continued Bertha.

There was a line of little wooden fishermen’s boats where the beach met the road.

“You, boy!” ordered Helene. “You come with me!”

Gertrude sensed fear. These two were spooky at the best of times. She wanted to go with Eric and began following him as he moved off.

“WHOOP!” she hooted.

“Control that monkey or I will put a bullet in its brain!” ordered Bertha.

Sid held the ape back. Eric felt this was not the moment to correct her mistake.

Under Helene’s direction, the boy was ordered to heave the rowing boat down to the shore. With machine guns trained on them at such close range, escape was impossible. Our three heroes climbed into the boat, followed by the twins.

“Now row!” barked Bertha.

With Gertrude sitting between them, Sid and Eric rowed the boat out to sea.

It was punishing work, fighting against the waves, but they made progress. The Nazi U-boat, which was bobbing up and down in the stormy sea, was now lined with what you might describe as a welcoming committee. A number of the submariners were standing to attention on the deck.

At the front was the captain: a handsome man with bright blue eyes and blond hair. He wore a roll-neck sweater and a peaked cap with a badge of an eagle holding a swastika.

On seeing Sid and Eric, he looked surprised. On seeing the gorilla, he burst out laughing.

“Ein Gorilla? Ha! Ha! Ha!”

It was clear he was not expecting to see her. Or, indeed, this little boy or old man.

The three prisoners were ordered out of the rowing boat. Sid and Eric looked back to the twins.

“No funny business!” snapped Bertha, brandishing her machine gun.

As soon as the three jumped on to the deck of the submarine, three brutish submariners grabbed them roughly by their arms.

Next, the twins stepped aboard. They shared a Nazi salute with the captain and chanted, “Heil Hitler!”

The captain whisked off his cap and bowed. Then he kissed both the twins on their hands, in a show that said he held them in the highest regard. The Brauns blushed at this gentlemanly display.

There was then a long conversation in German between the captain and the twins. From their looks and gestures it was obvious they were discussing the three prisoners. After a final nod from the captain, Sid, Eric and Gertrude were bundled down through the hatch and into the hull of the U-boat.

Soon everyone, including the Braun twins, was inside, and the ladder was pushed back up into position above.

Immediately, Eric felt a curious mixture of fear and excitement. He felt guilty for feeling excited, but he was an eleven-year-old boy on an enemy submarine, and it was exciting! Eric was sure to be the only British boy ever to have set foot on a Nazi U-boat.

But would he live to tell the tale?