It was ten o'clock in the morning of Christmas Day when twenty-five-year-old Peter Shaw entered the car park at Heathrow Airport, hunched his shoulders and gazed around at the rows of parked vehicles. There were family cars in profusion, a number of four-by-fours, a fair number of Jaguars and a couple of Rolls Royce limousines. Not for the first time, he wished that he had gone where the owners of those cars had gone. But on the pay he was getting, there wasn't much chance of that.

Anywhere would do. A sunny beach with a gorgeous girl, or a luxury cruise around the Caribbean; anywhere to get away from the cold of an English winter and this mind-numbing job. He didn't really know why he carried on doing it; he wasn't married and his on-off relationship with a girl who worked in one of the shops in Terminal Three was about to become permanently off.

With a sigh, he began his patrol. On five out of every seven days or nights, year in and year out, apart from his annual two weeks holiday, Shaw had walked this same car park at London's Heathrow Airport. His mundane task was to check cars that had been there longer than they should have been, and to make sure that none had been broken into or vandalized. Occasionally, he had found unlocked vehicles containing quite valuable property that the owners had carelessly left behind.

The only bit of excitement was likely to be the sighting of a suspicious character loitering near the cars. Then he would call his control room and they would send for the police.

At first, he had passed the indigo blue Jaguar XJ, but then he stopped, realizing that there was someone in the driving seat. He retraced his steps, moved closer to the car and tapped on the window. Receiving no response, he tried the door and found it unlocked. He pulled it open, and the body of a woman fell towards him. She was an elegantly dressed blonde in a smart grey trouser suit. Her jacket was undone, and Shaw could not fail to see that the front of her stylish silk blouse was soaked in blood.

'Bloody hell!' exclaimed Shaw. Shaking almost uncontrollably, he took an involuntary step back. For a moment he stared transfixed at the body, now lying half out of the car, head almost touching the ground. In a grotesque image of death, the woman's eyes were open, and her long blonde hair was hanging down.

Moving well away from the car, Shaw unclipped the personal radio from his waterproof jacket. 'Hello, control,' he said, and then muttered, almost incoherently, 'I've just found a dead woman in a car.'

The operator at the control room asked for details, and Shaw, agitated by what he had found, eventually managed, somewhat disjointedly, to explain the circumstances of the grisly scene he had chanced upon.

'Stay with it, Pete,' said the operator. 'I'll call the police. Meanwhile, don't let anyone near it.'

'Yeah, right, mate.' Shaw looked around, but the car park was deserted. There was no one to go near the body, just rows of silent vehicles, a dead woman and him. He moved as far away as possible and sat on one of the metal barriers.

Christmas should be a time of joy and understanding and Christian charity, or so we are told. It is a season of goodwill, of good things to all men, and all that sort of claptrap. So how come that there's nearly always a murder on Christmas Day? Where, I ask you, is the goodwill in that?

Well, if there is to be a murder, fate being what it is, the investigation is bound to fall to Detective Chief Inspector Harry Brock of Homicide and Serious Crime Command. I know this because I am the said Harry Brock and I'm assigned to HSCC West, a Scotland Yard unit that takes in that segment of London that stretches, wedge-shaped, from Chelsea out to Hillingdon, and all the hotbeds of villainy in between. Unfortunately, it also includes Heathrow Airport, otherwise know to us of the CID as Thiefrow.

My girlfriend Gail Sutton and I had decided to spend this particular Christmas Day at her town house in Kingston. Although in a relationship for a number of years now, we had agreed not to get married, probably because we'd both been married before. And each of those marriages had ended with a measure of bitterness all round.

In my case, I had been married to Helga Büchner, a German girl who, at the time, was a physiotherapist at Westminster Hospital. She had pummelled my wrenched shoulder back to mobility following a somewhat violent disagreement with a group of yobs in Whitehall when I was a uniformed PC. It had been a whirlwind courtship, followed by a marriage that my colleagues at the nick said wouldn't last, even though it had taken sixteen years for them to be proved right in their forecast.

It had effectively come to an end when our four-year-old son Robert had drowned in a pond. Helga had insisted on continuing to work after he was born, and had left the boy with a neighbour, as she had often done.

It had not been a happy marriage, but that tragedy had signalled an end to it. Adultery on both sides became the norm, followed inevitably by divorce when Helga announced that she wanted to marry a doctor at the hospital where she worked, and with whom she'd been having an affair for several months. The only advantage for me that had accrued from the match was that I'd learned to speak German fluently. On reflection it would have been better and cheaper had I gone to night school.

Matters improved significantly when I met Gail Sutton. Gail is an actress when she's not resting, as thespians call unemployment in 'the profession'. Her marriage had endured for far shorter a period than mine, but had ended for a similar reason. Her former husband, Gerald Andrews, was a theatre director. One day Gail, feeling unwell after the matinee, arrived home early and unexpectedly from the playhouse where she was appearing, to find her husband in the marital bed with a nude dancer. That was the end of the marriage, and Gail reverted to her maiden name of Sutton.

Andrews, however, had held an unreasonable and spiteful grudge against Gail, as though that unsavoury incident had been her fault rather than his, and he did his best to prevent her getting any decent parts thereafter. When I'd met her at the Granville theatre, she was hoofing it in the chorus line of a second-rate review called Scatterbrain, and I was investigating the murder of one of her colleagues.

Not that Gail has to work. Her father George is a rich property developer who lives in Nottingham with his wife Sally, herself a former dancer. George's two obsessions are Formula One motor racing and the land speed record, both of which he talks about incessantly. Until his wife tells him to shut up. But he gives his daughter a substantial allowance, and that is why Gail doesn't have to work. But, loving Gail as I do, I'm willing to listen to his land speed stories for as long as he's prepared to bore me with them.

On this particular Christmas morning George was in full flow. He and Sally had arrived the previous day to enjoy Christmas dinner with Gail and me. Gail and Sally were in the kitchen preparing the meal, and my only chore was to keep their glasses constantly topped up with champagne, and George's with whisky.

Gail had decorated the sitting room tastefully, but minimally. There was none of the paper chains that my late father favoured. I still remember spending hours as a child sticking the damned things together before my father strung...