1 hour 14 minutes 23 seconds remaining…

'Karl!' Hard as flint. Shrill enough to compete with the seagulls patrolling overhead. 'Karl! Don't!'

It was another Karl who answered; no more than ten years old, with ice cream spilling down the front of a bright red jumper. A hand lashed out, the other Karl began to cry. The wind carried Dresner's name away along the Thames; he turned back to face the river. It seemed, for a moment, as though the gulls had taken up the shrieks - they wheeled and twisted above the water, picked at pieces of debris, and danced over the froth churned up by a motor barge.

It was too late. An hour earlier, perhaps even half an hour if he had been lucky, and there would have been time: time to catch the train at Paddington and get back to the hotel; time to pack and check out; time to get to Heathrow and then on to Munich and still catch the holiday flight with Heidi. He stopped at a café and rifled through the tour guide, but left with a coffee half-drunk and the list of attractions stuffed back into his pocket.

He walked alone amongst the crowds until he saw the first sign for a station, without noticing which station it was. The tiled concourse was bordered on three sides by cafés and shops, on the fourth side by a line of ticket counters. To his right he noticed a sign for a pub – The Railway Hero.

Suddenly, Dresner longed to get very drunk. Anything to dull the senses.

As he pushed the door open a woman was coming the other way. Dresner stepped back to let her out. She was wearing a halter-neck top. A pool of perspiration glistened in her cleavage; the strap of her shoulder bag had carved an angry red ridge in the skin over her collar bone.

'What are you looking at?' she said.

'You-'

'I can do that myself.' She spoke through gritted teeth and grabbed at the door Dresner was already holding. She pushed past.

You remind me of someone, he wanted to call after her.

The pub was a fake: a few tables, a bar and a barman squeezed into one end of a shabby room, a one-armed bandit below a dartboard. The rest of the space was taken up with a Happy Traveller café. Dresner ordered the first thing he saw on the chalkboard menu – burger, chips, onion rings, side salad. He drank two export-strength beers while he waited, a third as he ate and rifled through a discarded tabloid.

BASTARDS! The word blazed from the front page, over a scruffy line of shops on a street littered with wreckage and marked by police tape. A child smiled from an inset picture, another showed a man and a woman standing by a grave. A topless model grinned from the next page – Dannii, 19, from Winchester.

Dresner needed the toilet by the time his plate, and glass, were empty. The Gents beside the one-armed bandit was stamped with an Out Of Order sign, below a Buy British advert on a Union Jack background faded almost into oblivion. The barman called out a muted thank-you as he left. Outside, a crowd of Japanese clustered in front of a timetable, a camera around every neck.

Nearby, a stall on wheels was stacked with pendants, earrings and ankle bracelets. A sign on top, in red letters on a yellow background, advertised Lucky Elephant Charms at 50p each.

'I didn't know elephants were lucky,' said Dresner to the woman hunched over a magazine on a chair beside the stall.

'Neither did I,' said the woman without looking up. She tapped a cigarette and gave the Japanese by the timetable a sideways look before returning to the headline on her lap: I Married My Husband's Murderer.

'Do they work?'

'Does what work?'

'These.' He picked one of the trinkets up.

'Search me. Buy one and see.' As he was reaching into his pocket, she added, 'It's three for a pound.' When he paused she said, 'Three times the luck.'

'Do I get my money back if they don't work'

'Don't make me laugh.'

'Sold much today?' Dresner asked after he'd paid. The woman licked a finger, turned a page, and sank back into a world of murder, jealousy and deceit: Forced To Wear A Chastity Belt – SO MUM KILLED HIM.

39 minutes 7 seconds remaining...

A queue trailed from the main toilets on the concourse. Dresner tried each platform in turn: more locked doors, more Out Of Order signs, until he found one in the murk of a cul-de-sac that looked like it hadn't seen a soul in decades. His head was beginning to spin and the food was repeating back up his throat. A warm, moist stench greeted him and he swore under his breath. Standing at the urinal, he tried not to breathe in, while behind him, from one of the two cubicles, came the noises of an occupant.

Water - steam almost - spurted out of the hot tap, then stopped after a few seconds. Nothing happened when he held his hands under the dryer vent. He flicked the plastic cover up and down and slammed his fist against the metal case: nothing.

'Can you pass me some toilet paper, please?' he said in the direction of his invisible companion.

'Use the dryer.'

'It's not working.'

'It was OK first thing.'

'It's not OK now.'

'You're not expecting me to fix it are you? I'm on me break. Tell Jimmie about it.'

'Who's Jimmie? I only need a piece of toilet paper.'

'You are Staff aren't you?'

'What?'

'Staff. S-T-A-F-F. This khazi's Staff Only...ah, fuck it. Here.' A sheaf of what looked like rice paper emerged.

'Thank you.' Dresner slammed the hand dryer once more as he walked out; this time it howled into life.

'Told you it were OK.'

But Dresner wasn't listening. He had caught the final words of a tannoy announcement drifting along the lifeless platform, telling people to move immediately to the nearest exit, telling people not to run, telling people to remain calm. The pigeons above his head kept cooing. Dresner leaned back and pushed the toilet door ajar. 'Security alert. They're telling everyone to get out.'

'It's a hoax. Had three of them last week. Fucking joke.'

'But we have to-'

'We don't have to do anything, pal. They'll all be back in ten minutes.' Something rustled; newspaper, maybe. 'You can go if you want to. I'm staying put. Now piss off and leave me alone.'

Dresner let the door slam shut. Snakes of commuters, with no obvious sense of hurry, slid along the platforms and up the steps towards the exit. People in uniform were shepherding, arms waving. From a speaker close by, the same message repeated and repeated, a weariness in the recording. The pigeons kept cooing. His head began to spin again and he thought he might be sick. By the time he came to climb the steps the other platforms had fallen silent and still. He held onto the hand rail as he climbed and then he made his way along the tunnel alone.

He tried to find a side exit, became confused, followed a sign that led to a dead end with a lift and an escalator down to the Underground. He shook his head and rubbed his eyes, found a bench and sat down. There's no rush, he told himself, they had three of these alerts last week: it's routine. There's no danger. And he had the lucky charms rattling in his pocket.

The bench was hard and uncomfortable. There was a better place to wait the scare out.

10 minutes 53 seconds remaining…

Like debris from a shipwreck floating on a sea of tiles, luggage littered the concourse. The Lucky Elephant woman had taken her cash box with her. Dresner wondered if the evacuation here had seemed more urgent. Far more than the railwayman's promised ten minutes had elapsed. The tannoy crackled and clicked, as though the announcer was clearing his or her throat; waiting, as Dresner was himself, for the tide to return, for the blip in normality to end. Nausea launched itself in waves again. He felt like the last man alive; the crowds outside had been pulled back out of sight. All of the information boards displayed the same message:

Security Alert. Please Evacuate The Station.
Security Alert. Please Evacuate The Station.
Security Alert. Please Evacuate The Station.

Dresner tried to make himself comfortable in the fake ambience of the Railway Hero. Being seated made him feel better, the stale scent of hot pastry, lager and beefburgers made him feel worse. He slung his feet up on a table, pressed his back to the wall and tried to curl up in a way that made his guts settle and his head spin less.

A series of shouts jolted him. His chair overbalanced, but the wall stopped him from crashing onto his back. Voices were coming from the direction of the steps up to the tunnel over the platforms. Perhaps this is it, he thought; perhaps they're letting everyone back in, panic over. He thought about catching a train, getting back to the comfort of his hotel bed, the comfort of a clean bathroom smelling of pine.

58 seconds remaining…

Footsteps, running footsteps, were approaching. Dresner stumbled out onto the concourse. He was sure he was going to be sick; the sudden standing up had done it. He recognised a voice, clearly heard in a silence interrupted only by the clicking overhead of the lifeless tannoy.

'I was on me break!'

A church bell tolled from the direction of the Thames. Two men were approaching: one, a policeman; the other, a rail worker with a cup of tea in one hand and a newspaper in the other. Dresner leaned over to vomit behind the Special Offer sign for the same burger meal he had eaten only a short time before.

'Come on, come on, come on,' the policeman was saying. 'Run faster, run faster! This is for real!' Then he appeared to stop in mid-stride. 'You!' he shouted at Dresner, pointing. 'What's wrong with you people? Get out! Now! Move it!'

Dresner held up a pacifying hand; he was still vomiting. He could feel there was more to come. The policeman opened his mouth to speak again, but Dresner never heard his voice. He saw the lips frozen open, at the moment of speech, but he never heard the voice. Instead he heard a sound, or the beginning of a sound.

From down amongst the maze of platforms came the thud of a heavy object being dropped, the sound of a pile-driver, the sound of a giant bass drum being struck by a giant object. There was no drama to the sound, it was a very simple sound: a single bass note with a sharp beginning, a sharp end and no echo. A silence, deep and empty, followed.

The blow to Dresner's chest squeezed the breath from his lungs. This can't be happening. I shouldn't be here. The air rippled as though a stone had been thrown into water. The policeman's mouth was moving, but no words were coming out. One by one, each window in the station concourse began to peel outwards and transform from panes of glass into a blizzard of knives.