Come on, Tina, ran.

The concrete shook.

Run.

Her hand slid into her pocket, fingers curling round the key. Her boots beat a regular rhythm on the ground. She skidded over the last few metres, but it didn't matter, she was there. Open up! Hurry!

The key slid out of her hand.

Oh no! she thought, please no, not now.

Frantically she fumbled for the key, spinning round in a circle.

The sky filled with darkness.

Slowly she looked up and saw the wave.

The hurry was over. She knew it was too late. She'd lived fast, and she'd die fast too. At least, she hoped it would be fast. At times she'd asked herself what it would be like to die, what went through a person's mind when their fate had been sealed and they knew it was time. I've come for you, Death would say. You've got five more seconds, so have a last think, whatever von like. Look back on your life, if you wish.

Didn't they say that as your car flipped over, or you fell from great height, that somehow, your life flashed before you, images from your childhood, your first love, like a 'best-of compilation?

But the only thing Lund felt was fear that death would hurt her, and she'd suffer. She felt almost ashamed that it had had to end so pitifully. That she'd messed up.

She watched as the tsunami crashed into Kare Sverdrup's restaurant, smashing it to pieces and surging onwards.

The wall of water reached the car park.

A few seconds later it was rushing up the hill.

The shelf

By the time the wave had reached the surrounding coastline, it had wrought untold damage on the shelf.

The oil-rigs and platforms built near the break had disappeared along with the slope. That alone had cost the lives of thousands but it was merely a foretaste of what was to come. As the water surged forward, it formed a towering vertical front that grew taller as the water depth decreased. Under the force of the impact the struts of the platforms snapped like matchsticks. In less than fifteen minutes more than eighty had toppled into the sea. The problem wasn't so much the height of the wave – North Sea oil platforms were built to contend with forty-metre waves, which, statistically speaking, occurred once in a hundred years – but the combination of other factors.

Even ordinary waves had been known to exert pressure of up to twelve tonnes per square metre – enough to rip out sections of harbour wall and deposit them in the centre of town, to throw sailing-boats into the air, and break a freighter in two. That was the impact of a wind-generated wave. The force of a tsunami was a different matter. Next to a tsunami of similar amplitude, even the most ferocious surface wave seemed gentle as a lamb.

The tsunami triggered by the landslide reached the middle of the shelf at a height of twenty metres, low enough to pass beneath the platforms' decks.

The force with which it hit the pilings was all the more lethal.

Oil-platforms, like ships and any other construction destined for long-term exposure to the sea, were expected to withstand certain stresses, which were measured in years. If the defining criterion was the forty-metre wave, then engineers designed the platform to survive the impact of the swell. Since the wave was expected only once a century, the platform – according to the workings of a none-too-confidence-inspiring logic – was deemed to have satisfied the hundred-year standard. That meant, statistically, that it was fit to weather a century of waves. Of course, no one expected it to last a hundred years being battered by forty-metre waves. In fact, it might not even survive one major surge. Monster waves weren't really the problem: the damage was done by everyday wear and tear caused by ordinary waves and currents. Platforms and other technical structures soon developed an Achilles' heel, although its location was anyone's guess. If a weak spot on a platform suffered the equivalent of fifty years' stress within the first decade, an ordinary wave might suddenly pose a risk.

Figures couldn't solve the dilemma. The statistics and mean values used in marine engineering described ideal scenarios, not what really happened. Averages might mean something to bureaucrats and engineers, but the sea had no truck with statistics: it was a succession of unpredictable circumstances and extremes. A particular stretch of water might have an average wave height often metres, but if you were hit by a one-off thirty-metre monster that statistically didn't exist, the average would be of precious little comfort: you would die.

When the tsunami swept across the landscape of steel towers, it exceeded their maximum strain. Struts snapped, welded joints burst open and decks sagged. On the British side, where steel structures were the norm, practically every platform was smashed to pieces or fatally damaged by the impact.

Years earlier Norway had switched to reinforced concrete pilings, which provided less of a target for the tsunami, but the outcome was no less calamitous: the wave bombarded the derricks with ships.

Theoretically, most ships weren't equipped to deal with surface waves of more than twenty metres. The hull-girder stress was designed to cope with a maximum nominal wave height of sixteen and a half metres. In practice, things worked differently. In the mid-nineties rogue waves north of Scotland tore a hole the size of a house in the 300,000 tonne tanker Mimosa, but the ship got away. In 2001 a thirty-five-metre breaker nearly sank the cruise ship MS Bremen off the coast of South Africa – nearly. That same year, close to the Falklands, the Endeavour, ninety metres in length, fell victim to a phenomenon known to oceanographers as the 'Three Sisters' – three freak waves, each thirty metres high, in quick succession. 'The Endeavour was severely damaged, but she made it back to port.

In most cases, though, the ships that met with freak waves were never seen again. Each monster wave would push a deep trough in front of it, a chasm that the vessel would sink into, bow or stern first. If the waves were far enough apart, there'd be time for it to rise up and scale the crest. When the wavelength was shorter, events took a different turn. 'The ship would pitch forwards into the trough, only to be met head-on by the vertical front of the following wave. The vessel would be swallowed and buried under water. Even if it managed to rise up from the trough and start to ascend the crest, there was still a danger that the wave would be too high or too steep. Most of the time it was both. Extremely high and extremely steep. 'That meant attempting the impossible – scaling a vertical wall. Smaller vessels in particular would fall victim to waves whose height exceeded their length, but even ocean-going giants didn't always make it out of the trough and over the crest. 'The wave would flip them over and they would hit the water upside-down.

Freak waves, generated by the interplay of currents and wind, could reach speeds of fifty kilometres an hour, but seldom more. That was enough to wreak havoc, but compared to the twenty-metre-high tsunami that was sweeping the shelf, a freak wave was a lame duck.

Most of the tugs, tankers and ferries that had the misfortune to find themselves in the North Sea at that moment were thrown around like toys. Some collided, others were hurled against the concrete pillars of the platforms, or smashed against the loading buoys to which they'd been moored. Even reinforced concrete couldn't withstand the force of the impact. The giant structures began to collapse. The few left standing soon followed suit. Tankers, some fully laden with oil, collided and exploded, smothering the platforms with clouds of fire. Derricks were blown to pieces in a series of chain reactions. Burning debris was scattered over hundreds of metres. The tsunami tore the platforms from their foundations on the seabed and toppled them into the water. The devastation of the shelf took place just minutes after the wave had surged outwards from the site of the submarine slide on its way to the coastline around it.