The driver of the big black Mercedes sees us first, before the officers who are seated behind him, and before Hitler, who is looking out, smirking now, at the cheering crowd.

I look at the driver and a puzzled expression crosses his face. The car’s not travelling fast, so he has plenty of time to brake as he gets closer. The sudden slowing of the vehicle causes Hitler to jolt forward, grab the top edge of the windscreen and look crossly first at his driver, and then ahead at me and my brother.

There can’t be many people alive who have seen Adolf Hitler in real life. (I know: you’re probably thinking, Well, neither have you, but it really feels like I have.) He’s shorter than I expected and his face is fleshy and pale. The little square moustache is unmistakable, though, and his cold blue eyes are furious at this interruption to his parade.

The next few moments appear to pass in slow motion.

The driver gesticulates angrily with his arm and barks at us, but I don’t understand a word: they are probably ones that Miss Linton won’t ever teach us. At the same time, two of the officers from the car leap out and start coming towards Seb and me.

‘Now!’ I shout. ‘Fire!’

Together we pull the triggers of our guns, unleashing a volley of orange sponge darts at the man they called the Führer. Our aim is rubbish, though: most of the darts ping off the windscreen of the car, leaving Hitler startled but clearly unharmed. A gasp goes up from the crowd.

‘Look out!’ I yell at Seb. Then, ‘Reload!’

On my command, the guns reload automatically, and we turn and fire a burst at the soldiers coming for us. This time our aim is better: the men go down, clutching their heads in pain.

Only in a dream could sponge darts be that effective!

The atmosphere in the crowd has changed in seconds. They watch in amazement as Seb and I run closer to the car, firing our toy guns at the uniformed officers, who have extracted their own pistols, but seem uncertain of how to proceed against two boys. One of them looks at Hitler as if for guidance, but Hitler continues to glare at us in silent astonishment.

This is even more fun than I had expected! I glance over to Seb: he has already downed the SS officer in a burst of orange missiles and is ready for another go at Hitler.

I raise my gun, tasking careful aim at Hitler’s moustache.

‘Okay, Adolf – get ready for one right in your gob!’ I shout.

My finger is squeezing the trigger when, from behind me, a large arm in a grey sleeve thumps down on the barrel of my gun, causing the ground in front of me to be peppered with orange foam. My assailant’s other arm grabs me in a chokehold and yanks the Nerf gun from my grasp, throwing it to one side.

I am caught, and immediately think about the Emergency Escape procedure. But before I can say anything I hear Seb scream from the other side of the huge motor.

‘Get off me!’

A huge soldier drags him, hand clamped over his mouth, his feet kicking up sand, until we are standing together facing the big black car, as Adolf Hitler climbs down and walks towards us slowly, his hands clasped behind his back, a cold half-smile on his damp lips. Following a pace behind is a stern-looking female SS officer, her cap pulled low, shielding her face. She is wearing the familiar black uniform, complete with the red-and-white armband featuring the hated Nazi symbol of the swastika.

She speaks first. ‘Silence! Ach so! Ve have a pair of Englishers, ja? In the uniform off the wunderbar Hitler Youth!’ She indicates me. ‘Do you see, mein Führer?’

Hitler nods solemnly, looking me up and down.

‘Ja, Kapitän Becker. Jawohl!’

This is good stuff. These people are talking exactly like the Nazi officers in Fit Billy’s film. For the full effect, the woman officer should click her heels together …

And she does. Then she takes off her cap, and angrily tosses her purple dip-dyed hair. I splutter with laughter when I realise she looks exactly like Kez Becker, and Hitler glares at me.

Seb cocks his head to one side and sticks out his tongue at Der Führer. ‘I’m not scared of you! You’re a big bully with silly hair and a stupid moustache and … and a rid-ridinkulous salute! Look!’ Seb imitates the Nazi salute and then waggles his fingers wildly, adding a big, wet raspberry through his missing teeth for good measure.

Hitler pale face turns pink. He purses his lips and narrows his eyes into an expression of pure fury and he barks a command.

The female officer leans forward and points to the letters SS on her collar.

‘Ha, my little friend! Do you know what these letters stand for?’

Thanks to Fit Billy’s obsession with World War Two, I do. They stand for Schutzstaffel – Hitler’s dreaded Nazi paramilitary police force. But I don’t know if Seb knows. (Nor do I like the way things are going. Bravery and excitement are all very well, but I am getting very close to calling it quits with the Emergency Escape.)

Seb peers at the letters and adopts an innocent expression. ‘SS?’ he says, and then he pauses for comic effect. ‘Are you a member of the Secret Seven?’

It takes a second or two for the SS officer to register what Seb has said, then she screams the German word for ‘no’, ‘Nein!’

‘Nope. I’ve read the books,’ says Seb. ‘I’m pretty sure there’s only seven.’

‘Insolence!’ she hisses. ‘Mein Führer! We must make an example of these English boys!’

Hitler nods solemnly and waves his hand casually as if to say, Get on with it then!

‘Very well. Bring it out.’

The officer strides to the rear of the big Mercedes and pops open the boot. Nothing happens for a moment, then a long crocodile flops on to the ground and uncurls itself, turning its head until it faces me.

I recognise it immediately and a chill goes through me from my skull to my toes.

Cuthbert.

This is not in the plan.