3:05am. The first indication came as the yellow sodium glow of street lamps flickered off. A dank, heavy atmosphere seemed to descend over the darkened streets of St Albans. Every waking person and animal sensed the chill through some dormant instinct. A shiver of fear prickled the attention of a tortoiseshell cat sitting on the garden fence on Partington Road. Fur fluffed and body tensed, it waited for an attack that never came.

Instead, the air was pierced by a loud noise and powerful spotlight beams as an army truck growled into the residential street. The cat’s pupils narrowed as it watched the bright lights trundle past the suburban semi-detached houses. A booming, amplified voice broke the stillness of the air as the truck passed by.

‘THIS IS NOT A HOAX… PLEASE GATHER BELONGINGS AND PREPARE TO BE EVACUATED… I REPEAT, PREPARE TO BE EVACUATED… THIS IS AN EMERGENCY…’

Within seconds, bedroom lights along the street were being tested, but the power had died. Bedroom windows opened and rudely awakened residents looked out into the street to identify the source of the disturbance.

Barely visible in the dark, khaki-clad soldiers marched down the street. A dozen or so men began to knock on doors, shouting the same message.

‘THIS IS AN EMERGENCY – GET DRESSED AND PACK CLOTHES NOW. BRING YOUR PASSPORTS.’

The cat scrambled hurriedly as a dark figure barged the gate of Number 22 open and rattled the green, wooden door knocker with full force.

‘GET UP NOW!’ he yelled.

Imogen sat up in bed and rubbed her eyes, unsure of what was real and what she had dreamt, just as her stepfather banged the door open. Generally a laid-back and genial man, the contrast in his demeanour showed Imogen that Ian Sampson meant business.

‘Immy, you have to get up! We have to go!’

‘Wha…’ she moaned in reply.

‘Just get dressed, quickly… There’s been some sort of disaster.’

Imogen’s eyes opened fully and she stared back. ‘What sort of disaster?’

Her stepfather paused momentarily but was not in a mood to prevaricate. ‘I don’t know. Maybe there’s been another explosion at the Buncefield oil depot.’

And then the door slammed shut. Imogen remembered well the fire at the local oil storage plant in 2005. She was ten at the time and had gazed, open-mouthed, as the sky turned black for days. The entire neighbourhood was evacuated to a church hall some miles away. Maybe that’s what it was? She peeped through her curtains and saw the local residents, parents and children, running out into the streets, still pulling on shirts and shoes, some carrying suitcases.

Without a second’s thought, Imogen jumped up from bed. She dressed in jeans and a sweater then ran downstairs. Her mother was hastily cramming clean clothes into a holdall and shouting to her husband.

‘…but how long will we be gone?’

‘How the hell do I know?’ he responded irritably from an upstairs bedroom. ‘Just pack what you can and we’ll worry about that later.’

Ian walked back into his own bedroom and then stood for a moment, frowning. Christine looked questioningly at him.

‘What?’

‘I just don’t understand why we would need passports.’

‘Mum, this is a school day,’ moaned Imogen from the landing. ‘I have homework to hand in.’

Her mother looked anxious but did not know what to say. ‘We have to do this. That’s what they’re telling us, darling.’

‘We don’t even know who these people are,’ replied Imogen. ‘They could be anybody wearing soldiers’ clothes. Why should we take any notice?’

A sense of duty and obedience towards authority had been instilled into Christine Sampson from an early age, an impulse not shared by her sceptical daughter. The door banged once more.

‘Please, do as I say, Immy. Don’t argue. Get your stuff ready and let’s go. This is for our own safety.’

Seconds later, the family spilled out into the crowded street. Somewhere overhead a searchlight played out from a helicopter, flashing momentarily, highlighting the hastily-dressed residents of Partington Road. A hum of excitement was in the air, children thrilled at the sudden departure from routine. With radios poised, army personnel stood awaiting their next orders.

Nobody had long to wait. Trucks returned from both ends of the street, doors flung wide to accommodate the waiting people.

Imogen found herself sandwiched between two younger children she barely knew, while her parents sat opposite on narrow benches. There were perhaps twenty people, together with their bags, squeezed together in the vehicle, while soldiers herded people into a further three or four trucks down the road. The doors shut suddenly with a bang. The interior was plunged into darkness, relieved only by the light from the headlights of other vehicles shining through the cab. A small girl nearby cried for her mother. The diesel engine revved and lurched forwards.

A man leaned forwards and shouted out into the darkness. ‘What’s all this about? Won’t someone tell us?’

A faceless voice shouted back to him, devoid of emotion. ‘Wait til we get there. You’ll be briefed then.’

‘But where are we going?’ the man persisted.

The silhouetted outline of the soldier’s head appeared at the small opening to the cab.

‘No questions! Silence! Understand?’

There was a mumbled conversation from the cab. Then a plummier, more reserved voice – a senior officer, perhaps – spoke up. ‘Please listen, everybody. There is no cause for alarm. Just sit down and enjoy the ride. Everything will be explained to you later.’

How long she sat there, Imogen could not say. Her back ached and she desired nothing more than to be back in her own bed. Some fellow passengers closed their eyes and dozed, but nobody talked, not even an expression of anxiety. Why did they accept the situation so blandly?

She frowned and looked searchingly through the small window and out into the night. No friendly light from streetlamps was in evidence, though the first signs of dawn were stirring with the shadowed fluttering of birds. No traffic noise, just the roar of the heavy truck as it made its way along deserted roads. Where were the other trucks? Maybe they had gone another direction or been left behind? Maybe they were taking a different route? Worse, maybe they were going somewhere else? Were there other trucks emptying the houses in neighbouring streets? What was going on?

‘What you looking at?’ A girl’s voice next to Imogen took her by surprise. A cheeky, estuary accent – her family must be cockneys. In the half-light, she could see a plump, cheery face with a smattering of freckles and a bobbed black haircut that made her look plumper still.

‘I was wondering where we’re going.’ Imogen could not help whispering; somehow it seemed impolite to talk aloud.

The girl shrugged. ‘I don’t know, but it’s near an airport.’

It was true. Imogen could hear in the distance the low, buzzing whirr of a twin-prop aeroplane. She remembered the sound vividly from visiting an airfield with her parents and seeing acrobatic aircraft giving demonstration flights. These sounded deeper, more resonant.

The girl seemed to read her thoughts. ‘They’re big freight carriers,’ she said definitively. ‘My dad’s a pilot, so I know all about them.’

‘Is your dad here? Perhaps he knows where we are.’

The confidence seeped from the girl’s chirpy face. Suddenly she seemed very small.

‘Mum? Dad?’ her voice came in a subdued whisper. She scanned the faces, but no-one spoke.

‘Don’t worry,’ said Imogen, putting her arm protectively around the girl’s shoulder. ‘I’m sure they’ll be along soon. They’re probably in another lorry.’

The girl weighed this up and grinned bravely. ‘Yeah, of course. I bet we’re going to fly somewhere. Do you like flying? I do. My dad takes me places sometimes, when he can. He only goes to places in Britain, but it’s still great. He lets me go into the cockpit too.’

Imogen suppressed the slight shiver of fear she often felt when thinking of flying in an aeroplane. Her memories were bad: being travel-sick in a warm, claustrophobic and airless cabin, people staring as she held the sick bag tightly and stepped determinedly towards the toilet… She shook her head, as if to throw off the past like snowflakes.

‘I’ve seen you round at school,’ the girl added conversationally. ‘I’m Rosie.’ Rosie did look slightly familiar to Imogen. She was perhaps a year or two younger than herself.

‘I’m Imogen.’

‘Yeah, I know. Your mates call you Immy, don’t they?’

Imogen bridled at Rosie’s familiarity. ‘Yes, they do, but you’re not my friend yet.’

‘Oh!’ Rosie looked crestfallen for a moment, but recovered her cheek quicker than Imogen had anticipated. ‘Well, I’m the best mate you got here. We better get to know one another… Immy.’

Just then, the truck juddered to a halt, the engine still running. What looked like a checkpoint with a red and white barrier was in front of them. The cab door slammed. Voices – a muffled dialogue somewhere outside – then a slight creak of resistance before the barrier rose in front of the truck and the passenger returned to the cab. The truck drove on into a darkened area, though somewhere straight ahead bright lights shone from floodlight pylons as if a huge football match were in progress. The outline of a large building silhouetted against the lights stood between the truck and the light pylons, evidently their destination. It looked like a small airport, but nothing like Stansted or Heathrow.