‘Three kilometres,’ he grunted. ‘No petrol station there.’ Kate glanced at Stuart, who was staring at the floor beneath his feet. Three kilometres on a winding mountain road qualified as a suicide drive. ‘This is madness, Kate,’ Stuart muttered.

She didn’t demur. But what choice did they have?

Kate watched as the cars at the other booths moved off and were replaced. But the officer at their cubicle just stared at the screen in front of him, as he had been doing ever since he’d first swiped their passports through.

Time crawled by. Kate looked straight ahead, trying to project a nonchalance she certainly didn’t feel. ‘Get ready,’ she muttered, under her breath.

The Customs officer stood. ‘Stay here,’ he instructed. He stalked across to the low-slung grey stone building that appeared to act as the headquarters. As soon as he had disappeared from view, Kate began to accelerate gently.

Stuart glanced over his shoulder. It was only a few seconds until the officer re-emerged from the building opposite. And as he shouted an indecipherable warning to the armed guards sleepily leaning against the walls around him, Kate stamped hard on the accelerator.

Bullets shattered the rear windscreen. She hurtled down the narrow lane between the fence and the central crash barriers, pushing the beaten-up Lada for every ounce of its feeble horsepower. The barrier marking the official limit of Russian territory loomed. Two soldiers were rushing to stand in front of it, rifles raised. ‘Get down,’ Kate yelled.

Stuart appeared frozen, so she took hold of his hair with her left hand and yanked his face down towards the steering wheel a split second before bullets shattered the front windscreen and ricocheted off the bodywork.

The car hit the crash barrier, bounced into the fence, but kept its momentum. Kate sat upright again. She accelerated away just as another slew of bullets tore through the car, whistling past her head.

They were out in no man’s land; three kilometres of road winding down to the Georgian side, with a static queue of bumper-to-bumper traffic coming in the opposite direction.

At least one of the tyres must have been shot out. Kate had to fight to keep the car level as the rubber eventually shredded, then spun off.

Stuart straightened, looked behind them.

Kate kept her foot down, still wrestling to keep the car in the narrow gap between the queue of traffic coming towards them and a precipitous drop on the other side of the road.

They approached a tunnel. The car slewed towards the edge of the tarmac and it was all she could do to fight it back on course. She missed the wall at the entrance to the tunnel by centimetres.

‘Anyone there?’ Kate asked.

‘Not yet.’

The noise of the wheel rim against the tarmac was deafening. Kate slowed a fraction, then swung the car at the last moment into the front of a lorry that had been inching slowly forward in the queue on the other side of the road. Stuart exhaled in panic and shock. Kate unclicked his seatbelt and her own and grabbed the lapel of his leather jacket, wordlessly dragging him out of her side of the car.