Ever since her break-up with Mal, her esteem had been on the floor. At thirty-seven she was an attractive woman, and would be a lot more attractive, several of her friends and her late sister had told her, if she put back some of the weight she had lost. She was haggard, she knew: she could see for herself just by looking in the mirror. Haggard from worrying about everything, but most of all from worrying for over six years about Caitlin.

It was shortly after her ninth birthday that Caitlin had first been diagnosed with liver disease. It felt like the two of them had been in a long, dark tunnel ever since. The never-ending visits to the specialists. The tests. The brief periods of hospitalization down here in Sussex, and longer periods, one of almost a year, in the liver unit of the Royal South London Hospital. She’d endured operations to insert stents in her bile ducts. Then operations to remove stents. Endless transfusions. At times she was so low on energy from her illness that she would regularly fall asleep in class. She became unable to play her beloved saxophone because she found it hard to breathe. And all along, as she became a teenager, Caitlin was getting more angry and rebellious. Demanding to know Why me?

The question Lynn was unable to answer.

She’d long ago lost count of the times she had sat anxiously in A &E at the Royal Sussex County Hospital, while medics treated her daughter. Once, at thirteen, Caitlin had had to have her stomach pumped after stealing a bottle of vodka from the drinks cabinet. Another time, at fourteen, she fell off a roof, stoned on hash. Then there was the horrific night she came into Lynn’s bedroom at two in the morning, glassy-eyed, sweating and so cold her teeth were chattering, announcing she had downed an Ecstasy tablet given to her by some lowlife in Brighton and that her head hurt.

On each occasion, Dr Hunter came to the hospital and stayed with Caitlin until he knew she was out of danger. He didn’t have to do it, but that was the kind of man he was.

And now the door was opening and he was coming in. A tall, elegant figure in a pinstriped suit with fine posture, he had a handsome face, framed with wavy salt and pepper hair, and gentle, caring green eyes that were partially concealed by half-moon glasses.

‘ Lynn!’ he said, his strong, brisk voice oddly subdued this morning. ‘Come on in.’

Dr Ross Hunter had two different expressions for greeting his patients. His normal, genuinely warm, happy-to-see-you smile was the only one Lynn had ever seen in all the years that she had been his patient. She had never before encountered his wistful biting-of-the-lower-lip grimace. The one he kept in the closet and hated to bring out.

The one he had on his face today.

It was a good place for a speed trap. Commuters hurrying into Brighton who regularly drove down this stretch of the Lewes Road knew that, although there was a forty-mile-an-hour limit, they could accelerate safely after the lights and not have to slow down again along the dual carriageway until they reached the speed camera, almost a mile on.

The blue, yellow and silver Battenburg markings of the BMW estate car, parked in a side road and partially obscured from their view by a bus shelter, came as an unwelcome early-morning surprise to most of them.

PC Tony Omotoso stood on the far side of the car, holding the laser gun, using the roof as a rest, aiming the red dot at the front number plates, which gave the best reading on any vehicle he estimated to be speeding. He clicked the trigger on the plate of a Toyota saloon. The digital readout said 44 mph. The driver had spotted them and had already hit the brakes. Using the rigid guidelines, he allowed a tolerance of 10 per cent over the limit, plus two. The Toyota carried on past, its brake lights glowing. Next he sighted on the plate of a white Transit van – 43 mph. Then a black Harley Softail motorbike sped past, going way over the limit, but he wasn’t able to get a fix in time.

Standing to his left, ready to jump out the moment Tony called, was his fellow Road Policing Officer, PC Ian Upperton, tall and thin, in his cap and yellow high-visibility jacket. Both men were freezing.

Upperton watched the Harley. He liked them – he liked all bikes, and his ambition was to become a motorcycle officer. But Harleys were cruising bikes. His real passion was for the high-speed road-racer machines, like BMWs, Suzuki Hayabusas, Honda Fireblades. Bikes where you had to lean into bends in order to get round them, not merely turn the handlebars like a steering wheel.

A red Ducati was going past now, but the rider had spotted them and slowed almost to a crawl. The clapped-out-looking green Fiesta coming up in the outside lane, however, clearly had not.

‘The Fiesta!’ Omotoso called out. ‘Fifty-two!’

PC Upperton stepped out and signalled the car over. But, whether blindly or wilfully, the car shot past.

‘OK, let’s go.’ He called out the number plate – ‘Whiskey Four-Three-Two Charlie Papa November’ – then jumped behind the wheel.

‘Fuckers!’

‘Yeah, cunts!’

‘Why don’t you go chasing real criminals, right?’

‘Yeah, ’stead of fuckin’ persecuting motorists.’

Tony Omotoso turned his head and saw two youths slouching past.

Because 3,500 people die on the roads of England every year, against 500 a year who are murdered, that’s why, he wanted to say to them. Because me and Ian scrape dead and broken bodies off the roads every damn day of the week, because of arseholes like this one in the Fiesta.

But he didn’t have time. His colleague already had the blue roof spinners flashing and the siren whup-whooping. He tossed the laser gun on to the back seat, climbed in the front, slammed the door and began tugging his seat belt on, as Upperton gunned the car out into a gap in the traffic and floored the accelerator.

And now the adrenalin was kicking in as he felt the thrust of acceleration in the pit of his stomach and his spine pressed against the rear of the seat. Oh yes, this was one of the highs of the job.

The Automatic Number Plate Recognition video screen mounted on the dash was beeping at them, showing the Fiesta’s index. Whiskey Four-Three-Two Charlie Papa November had no tax, no insurance and was registered to a disqualified driver.

Upperton pulled over into the outside lane, gaining fast on the Fiesta.

Then a radio call came through. ‘Hotel Tango Four-Two?’

Omotoso answered. ‘Hotel Tango Four-Two, yes, yes?’

The controller said, ‘We have a reported serious road traffic collision. Motorcycle and car at the intersection of Coldean Lane and Ditchling Road. Can you attend?’

Shit, he thought, not wanting to let the Fiesta go. ‘Yes, yes, on our way. Put out an alert for Brighton patrols. Ford Fiesta, index Whiskey Four-Three-Two Charlie Papa November, colour green, travelling south on Lewes Road at speed, approaching gyratory system. Suspected disqualified driver.’

He didn’t need to tell his colleague to spin the car around. Upperton was already braking hard, his right-turn indicators blinking, looking for a gap in the oncoming traffic.