He sounded almost aggrieved, and I commented: ‘All the same, I think we should assume that they’re still alive.’

      ‘Should we? To be honest, Doctor, I’d rather you didn’t assume anything. That’s why I’ve asked you here.’

      He stared at me without hope, already regretting the decision. As we both well knew, the fact that I had been called in by the Home Office, after my unpopular minority report on the Hungerford killings, was less a compliment to me than a comment on the failure of the police, the CID and the intelligence services to come up with even a solitary clue to the sources of this horrific crime.

      As baffled as the Permanent Secretary, I could only think of asking his permission to visit the murder site at Pangbourne Village. The luxury housing estate was still sealed off from the press and public, but had been tramped over by an army of heavy-footed investigators. I waited as he scribbled my laissez-passer, my arms burdened by two Home Office briefcases loaded with their probably useless files. Then I remembered the comfortable seats of the viewing theatre in the Whitehall basement, and as an afterthought asked if I could see the police video recorded at Pangbourne within a few hours of the crime.

      ‘The police video? All right, but it’s pretty grim stuff. Though after Hungerford, I dare say you have the stomach for this sort of thing, Doctor …’

      Irritated by his tone, I almost declined. The senior people at both the Home Office and Scotland Yard regarded me as a dangerous maverick, overly prone to lateral thinking and liable to come up with one embarrassing discovery after another. Later, looking back as I revise these diaries for publication, I realize that it was there, in the deserted viewing theatre, that I was given my first glimpse into the real causes of the Pangbourne Massacre. If I failed to recognize what I saw, and if over the course of my investigation I seem unduly slow to identify the culprits, I can only plead that what now appears self-evident scarcely seemed so at the time. My failure to recognize the obvious, in common with almost everyone else concerned, is a measure of the true mystery of the Pangbourne Massacre.

       The Police Video

      Like millions of other television viewers, I had already seen selected extracts from the film in numerous documentaries about the massacre, and I hardly expected any sudden revelation. But as I relaxed in the viewing theatre, I soon realized what a remarkable film this was, and how well it conveyed the curious atmosphere of Pangbourne Village – in its elegant and civilized way a scene-of-the-crime waiting for its murder.

      The twenty-eight-minute film was taken by officers of Reading CID soon after eleven o’clock on the morning of 25 June 1988, some three hours after the murders. Thankfully, there is no sound-track, and one is glad that none is necessary, unlike the TV programmes with their hectoring commentaries full of lurid speculation. This minimalist style of camera-work exactly suits the subject matter, the shadowless summer sunlight and the almost blank façades of the expensive houses – everything is strangely blanched, drained of all emotion, and one seems to be visiting a set of laboratories in a high-tech science park where no human operatives are employed.

      The film opens by the gatehouse that controlled access to the ten mansions, the recreation club and gymnasium that made up the estate. The medallion of the private security firm is visible beside the visitors’ microphone, but there is no sign of the uniformed security guard who usually sat at the window.

      The camera turns to show the delivery van of the local wine-merchants which the police have parked among the ornamental trees on the grass verge. The driver, a pallid young man in his early twenties, is staring in a despondent way at the deep ruts left in the finely trimmed grass, as if the costs of restoring this once-immaculate surface will have to be met from his wages. It was he who gave the alarm, after discovering the first of the bodies as he delivered a case of white burgundy to the Garfield house (No. 3, The Avenue).

      The camera fixes on him, and like a badly trained actor he steps forward to the gatehouse, a tic jumping across his sallow cheek. He points to the door, and a uniformed constable opens the armoured glass panel to reveal the interior of the office.

      A security guard is lying on the floor below the row of television monitors, their screens a blizzard of snow. Someone has cut the cable running from the surveillance cameras mounted all over the estate, but clearly officer Turner had no time to reach for the telephone whose scissored cord hangs from the desk above his head. Arms pinioned, he lies within a bizarre contraption of rope and bamboo sticks, his neck gripped by a pair of spring-loaded steel calipers, as if in his bored moments he had been constructing a box-kite for one of the pampered children of the estate and had been trapped inside it.

      In fact, as I can see from the livid contusions on his throat, he has strangled himself after blundering into this lethal cat’s cradle which his murderer dropped over his shoulders, its double nooses tightening around his neck as he struggled to free his arms and legs.

      The camera leaves the gatehouse and sets off along The Avenue, the tree-lined central drive of the estate. The handsome mansions sit above their ample front lawns, separated from each other by screens of ornamental shrubs and dry-stone walls. The light is flat but remarkably even, a consequence of the generous zoning densities (approx. two acres per house) and the absence of those cheap silver firs which cast their bleak shadows across the mock-Tudor façades of so many executive estates in the Thames Valley.

      As well, though, there is an antiseptic quality about Pangbourne Village, as if these company directors, financiers and television tycoons have succeeded in ridding their private Parnassus of every strain of dirt and untidiness. Here, even the drifting leaves look as if they have too much freedom. Thirteen children once lived in these houses, but it is hard to visualize them at play.

      For once, unhappily, the pale green slopes of Parnassus are marked with a darker dye. The police camera turns to examine the Garfield family’s Mercedes in the driveway of No. 3. Roger Garfield, a merchant banker in his mid-fifties, sits in the rear seat, head leaning against the off-side stereo speaker as if to catch some fleeting grace-note. He is a large-chested man with a well-lunched midriff and strong legs that have spent agonizing hours on an exercise cycle. He has been shot twice through the chest with a small-calibre handgun. Almost as surprising, he is wearing no trousers, and bloodstained footprints emerging from the house indicate that he was shot while dressing after his morning shower. He somehow managed to walk downstairs and took refuge in his car. Perhaps his clouding mind still assumed that he would be driven to his office in the City of London.

      But the Mercedes was going nowhere. Garfield’s chauffeur had been shot dead a few moments after his employer. A white-haired man in a black uniform, Mr Poole lies face down in the bed of orange-tipped cannas beside the front door, cap still held in his right hand.

      The camera pauses over him and then enters the house, following the bloody footprints through the open door. Garfield and his wife had made numerous trips to Hong Kong, and the rooms are filled with pieces of chinoiserie – large porcelain vases stand on the blackwood furniture, and there are pairs of Ming horses and jade figurines. Surprisingly, none have been disturbed, suggesting that the murderers had approached their victims without surprise. The housekeeper, Mrs West, lies shot below the marble mantelpiece in the drawing-room, interrupted while doing her dusting. In an upstairs bathroom the camera finds Mrs Garfield, a handsome woman in her late forties, slumped against the glass door of the shower stall, her yellow toothbrush still in her hand.

      All trace of the Garfields’ sixteen-year-old son, Alexander, had vanished. His bedroom, study and bathroom were undisturbed. Only in his mother’s blood flowing across the bathroom tiles could be seen the smeared prints of Alexander’s rubber-cleated shoes, left behind as he was seized and swept away by his abductors.

      The police video continues on its grim and matter-of-fact way. The camera leaves Garfield seated in his Mercedes and gazes across the tranquil lawns at the next macabre tableau. As the two constables outside the Reade