‘I could kill you now,’ Kamal said. ‘Just for talking to me like that.’

‘Then you’d never find your way through the maze of tunnels down there,’ Ben replied. ‘There are a hundred hidden shafts, and as many false doorways.’ It was a wild bluff, but he needed to buy all the time to could to think of a way out of this. ‘You could spend years searching. Kill me, and you can kiss your private little jihad goodbye.’

Kamal’s voice was tight with fury. ‘Fuck you. Keep walking.’

‘You’re scared, aren’t you, Kamal? Scared shitless you’re not going to find anything down there. You know that the kind of people you’re buying these nukes from aren’t going to tolerate you not coming up with the cash. You thought you were the hardest, meanest guy in the world. But now you’ve done a deal with the devil, and you’re pissing your pants.’

Kamal was about to reply when another rumble groaned through the rock around them. A ripping crack echoed through the shaft. In the white torch beam, Ben saw a fissure open up to the width of a man’s thumb. Powder and dust cascaded from the ceiling, followed by a stream of small rocks that formed a pile up ahead.

‘What was that?’ Kamal asked, his fierce self-assurance slipping for an instant.

‘Something I forgot to mention,’ Ben said over his shoulder as he walked on, kicking rocks out of the way. ‘The tunnels are becoming unstable. Your treasure just slipped a little further out of reach.’ This time, it was no bluff.

Kamal quickly regained his composure, and laughed darkly. ‘Then there’s no time to lose. Move faster.’

Emad prodded the rifle hard into Ben’s back, shoving him onwards. As they rounded the bend in the tunnel shaft, the giant cavern opened up ahead and the torch beams picked out the shape of the rope bridge.

‘Keep moving,’ Kamal said.

More dust and stones showered down around them. It was getting steadily worse. Cracks were forming everywhere, slowly widening. The ridge was crumbling, with them inside.

Another painful jab from the AKS behind him, and Ben stepped out onto the bridge. ‘I don’t know how safe it is for four men to cross,’ he said truthfully.

‘Walk.’

Ben stepped forwards. The bridge gave a long, juddering creak under the extra weight as Emad followed, then Kamal, then Fekri. Ben held his breath and kept moving. The torch beams bobbed and danced ahead of him, throwing long tubes of light into the dark.

Dangling over a bottomless, spike-filled chasm, outnumbered three to one, unarmed with a gun in his back, no possibility of escape and time fast running out. He was sure he’d been in tougher situations-but he really couldn’t remember when.

Just then it got even worse. There was a grinding crack from somewhere high above them, and a huge dark shape hurtled through the beam of light ahead.

It was a falling stalactite, a solid rock spike, as thick as an oak tree, twice the height of a tall man. It narrowly missed the bridge. Seconds later it impacted on the stalagmites below with a roaring crash that shook the cavern and made the bridge sway alarmingly. Ben gripped the ropes at his sides and struggled to keep his footing. Fekri swore in Arabic. His voice was tense and frightened.

Then it happened again. A boulder as big as a large car plummeted not ten feet from where Ben was standing, and he felt the wind as it passed him. Another massive rumbling crash as it shattered into a million pieces on the spikes below. Smaller rocks rained down. A stone the size of a cannonball came crashing out of the darkness above and punched through the wooden slats of the bridge between Ben and Emad. Emad wobbled off balance, almost dropping his weapon as he grappled to stay upright.

Ben felt the impact’s shudder running under his feet the whole length of the bridge. He looked down, and in the dim light he saw one of the ancient ropes beginning to unravel. The outer strands splitting, slowly rotating and peeling away; then the next layer, and the next.

That was when he knew they weren’t going to make it across.

Crack.

They all looked up.

Fekri screamed.

Another giant stalactite had sheared off and it was plunging straight for them. Ben saw its craggy point looming up fast as it speared downwards. In the instant before it hit, he thrust the Maglite in his belt, looped his arm through the side of the rope bridge and held on tight.

Fekri was staring up, open-mouthed, as the massive spike caught him right in the face. It tore off his jawbone and kept going, lancing through his body, tearing him in two.

Then it crashed straight through the floor of the bridge and parted it like thread.

Ben fell through space. The wind roared in his ears as he sailed downwards. He had the rope in a death-grip. There was no time to pray, or even to think. Then a stunning impact as the severed bridge came swinging down and hit the wall of the abyss. Ben was winded for a few seconds, and it was all he could do to hang on. He blinked to clear his head and the pain that shot through his whole body.

He slipped the torch out of his belt and shone it upwards, hanging by one hand. The broken bridge had become a wildly swinging rope ladder, and he was dangling from it like a fly caught on a web.

He shone the light downwards, and his heart jolted.

Kamal’s snarling face was staring up at him. The terrorist had managed to cling on, and he was scaling the rope ladder towards him. Between them, Emad hung limply from the ropes. The impact had smashed his skull. His weapon had dropped into the depths.

Kamal hung by one hand as he grabbed the dead man’s belt and tore him forcefully from the ropes. The corpse somersaulted away into the darkness. A crunch as his fall was halted by the point of a stalagmite.

Kamal’s teeth were bared in hatred as he kept climbing rapidly upwards, his hands shooting up like pistons, one after the other. He made a grab for Ben’s ankle. Ben kicked out for his face, but Kamal dodged the blow. His hand went down to his belt and came up with a combat knife. He slashed at Ben’s legs with it. Ben drew his knees up just in time to avoid the blade, lashed out again and caught Kamal’s shoulder, driving him down several spars of the bridge. The terrorist screamed in anger and pain. The blade of the knife glinted as he flipped it over endwise in his hand, catching it by the tip between finger and thumb. He drew back his arm and hurled it straight at Ben.

The knife cartwheeled through the air. If it had been travelling horizontally it would have struck with lethal momentum, but the near-vertical trajectory robbed it of most of its kinetic energy and Ben just had time to twist out of its way. The sharp tip clanged and sparked against the rock an inch from his head and then spiralled away into the darkness. Kamal came on, punching and gouging. Ben swung down with the Maglite and caught him on the arm. Kamal cried out. Kept on fighting like a wild animal. The two of them swung crazily over the abyss.

At that moment the ropes gave way with a crack.

They hurtled down, locked together, the wind roaring in their ears.

Two seconds of freefall. Three. Four. Then another crashing impact as Ben felt himself hit a stalactite, narrowly avoiding being impaled by its point. He slid and bounced down its conical length. Rough stone tore at his flesh. Kamal’s hands were still locked on to him, punching and gouging frenziedly even as they plummeted to their deaths.

They hit the bottom.

And went plunging underwater with a stunning splash. Dazed by the impact, Ben felt his body go limp. But with the first gulp of cold water he came to his senses and started swimming for his life. Bubbles erupted from his lungs as for an instant he was panicking in the murk, unable to tell which way was up and which was down. Then he realised he was still clutching the precious torch. The light beam sliced through the water and found the surface. He kicked out hard, and let out a wheezing gasp as his head and shoulders burst free of the water.