He let the clip run on. Oliver’s breath was rasping out of the speaker as he staggered down the corridor. He stopped, swung round as if looking back to see if someone was following him. Nobody was.

Ben paused the clip again. He could see something. An alcove in the wall. Inside the alcove stood a statue that looked Egyptian, like a Pharaoh’s death mask.

Then the clip came to an end. Oliver must have turned off the camera. Ben was left staring at a black screen.

He struggled to understand what he’d seen. He clicked on the file properties. The video-clip had been created at 9.26 on the night Oliver died.

None of this made sense. The official version of the story, that Oliver had been drunkenly messing about on the lake with some woman he’d picked up at a party, was impossible to reconcile with the fact that, not long before his death, he’d witnessed a brutal ritualistic murder. Would Oliver have been capable of putting such a thing out of his mind to go off and enjoy himself? Who would?

Ben ran over what he knew. Oliver had witnessed a crime carried out by some highly organized and very dangerous people. He’d had evidence and he’d been desperate to hide it. Soon after he’d posted the CD to Leigh, he’d drowned in the frozen lake. The investigation into his death had been a little too rushed, a little too sketchy. And ever since Leigh had mentioned to a TV audience that she was in possession of Oliver’s notes, someone had been out to do her harm.

He looked down at Leigh as she slept and resisted the impulse to brush a lock of hair away from her face. Just as she’d been starting to come to terms with Oliver’s accident, she was going to have to go through the whole thing again-only this time knowing, almost for certain, that her brother’s death had been no accident. He hadn’t died messing around in a cheerfully drunken state. He’d died in fear. Someone had coldly and calculatedly ended his life.

Who did it, Oliver?

Ben moved away from the bed and settled into the armchair in the far corner of the hotel room. He reached for his Turkish cigarettes, flipped the wheel of his Zippo lighter and leaned back as he inhaled the strong, thick smoke. He closed his eyes, feeling fatigue wash over him. He hadn’t had a proper night’s sleep in four weeks.

His thoughts wandered as he smoked. He recalled fragments of old memories. He remembered Oliver’s face as a younger man, the sound of his old friend’s voice.

And he remembered the day, all those years ago, when Oliver had saved his life.

It had been the coldest winter he could remember. After three years of army service, Lance-Corporal Benedict Hope had travelled to Hereford in the Welsh borders along with 138 other hopefuls from other regiments for what he knew was going to be the toughest endurance test of his life. Selection for 22 Special Air Service, the most elite fighting force in the British Army.

Quite why Oliver had wanted to come along with him, Ben didn’t know. For the food, Oliver had joked. 22 SAS was famous for the mountains of roast beef and lamb chops on which selection candidates feasted before being sent into the hellish ‘Sickener 1’, the first phase of selection training.

As the convoy of trucks left the base in Hereford at dawn on day one and headed deep into the Cambrian Mountains of mid-Wales in driving snow, Oliver had been one of the only men able to joke about the long day ahead. Ben had sat in the corner of the rocking Bedford, cradling his rifle and steeling himself for the nightmare of physical and mental torture that would mark the start of the toughest few weeks of his life. He knew that the small minority who survived the initial selection process would be subjected to fourteen more torturous weeks of advanced weapons and survival instruction, a parachute course, jungle warfare training, language and initiative testing, a one-thousand-yard swim in uniform, and interrogation resistance exercises designed to stress a man’s spirit past the limits of endurance. Only the very best would get through to be awarded the coveted winged dagger badge and entry into the legendary regiment. Some years, nobody got through at all.

As it turned out, Sickener 1 was every bit as tough as he’d expected and a bit more. With each freezing cold dawn the number of exhausted men setting off for another round of torture dwindled a little further. Base camp each night was a huddled circle of silent bodies under dripping canvas. Oliver’s expectations of a nightly feast had been quickly dashed and his morale plummeted accordingly. That was the idea.

The following week was way beyond even Ben’s expectations. Weather conditions were the worst in years. Pain, injury and absolute demoralization had reduced the 138 men to only a dozen. During a twenty-hour march through a howling blizzard, an SAS major who had volunteered for the course to prove to himself he still had what it took in his mid-thirties had collapsed and been found dead in a snowdrift.

But Ben had willed himself to go on, trudging through the pain barrier and finding new heights of endurance. His only stops were to drink a little melted snow now and then and take a bite from one of the rock-hard Mars Bars he’d stowed in his bergen. The rush from the sugar gave his depleted body the energy to keep going. In his mind he fought a furious battle to quell the desire to give up this madness. He could end the agony at any time, just by deciding to. Sometimes the temptation was unbearable. That was also the idea, and he knew it. Every moment was a test.

And it didn’t get easier. Every night the exhaustion was worse. Back at camp he meticulously soaked his socks in olive oil to ease the torment of blistered feet, and he passed each day in a trance of grim determination as the marches got longer and their packs got heavier. All that mattered was the next step forward. Then the next. He kept his mind clear of the distance still ahead of him. And the pain that was only going to get worse.

By the fourth day of week three there were only eight men left. Pausing for breath on a high ridge near the summit of the notorious Pen-y-fan Mountain, Ben looked back and could see some of the others as distant green dots labouring across the blanket of snow between the trees far below.

Oliver was thirty yards behind him. Ben waited for him to catch up. It took a while. He was amazed that his friend had got this far, but now Oliver was visibly flagging. His steady trudge had deteriorated to a desperate plod and from there to a stagger. He sank to his knees, clutching his rifle. ‘You go on,’ he wheezed. ‘I’m whacked. I’ll see you at camp.’

Ben looked at him with concern. ‘Come on, there’s just a few miles to go.’

‘No chance. I can’t fucking move another inch.’

‘I’ll stay with you,’ Ben said, meaning it.

Oliver wiped snow from his eyes as he looked up. He coughed. ‘You will not,’ he said. ‘You need to keep moving. Go. Get out of here.’

Ben’s feet were stripped raw and he could feel his clothes stuck to the bleeding sores on his back where his bergen was constantly rubbing. It was all he could do to support his own weight. There was no way he could help Oliver walk very far, let alone carry him. And the slightest sign of hesitation could mean the humiliation of a Return To Unit order. The rules were brutal. They were intended that way. ‘You’ll be OK,’ he said. ‘There’s an instructor coming up the mountain. He’ll take you back.’

Oliver waved him on. ‘Yes, I’ll be OK. Now piss off before you get RTU’d. You want the badge, don’t you? Don’t wait for me.’

Racked with guilt now as well as pain, Ben walked on. The wind tore at his smock. He struggled down a near-vertical rocky slope, his boots slipping in the snow. He reached the ice-crusted rim of a collapsed rock mound and saw a movement through the mist of exhaustion. A hooded figure emerged from a clump of pines.