‘The lift won’t have survived this carnage,’ said Porter.

‘There’s another exit from there. If we can get through …’

Hassad started to lever himself up into the hole in the rock. There was enough room for a man to crawl through it – just – but not enough to carry Katie.

‘You push her, I’ll pull,’ shouted Hassad as he disappeared into the tunnel.

With a heave of his forearms, Porter hoisted Katie up to the mouth of the tunnel. He pushed her into position, ignoring the cry of pain as she smashed her elbow into the rock. ‘Just grab his hand,’ he shouted, struggling to make his voice heard over the crashing of collapsing timbers behind them.

Porter pushed her again, then pulled himself up into the vertical tunnel. It measured just three feet in diameter: enough space for a person to crawl through, but only just. The surface of the tunnel was pitted and rough, but there were plenty of places to get a grip on the rock. Using the muscles in his legs to propel himself forwards, his arms pushed Katie up. Hassad was dragging her along with his arms. It was hard going but they were making steady progress. Porter could hear a couple more explosions behind him but he reckoned most of the blokes down there must be dead by now. They were lucky just to have made it this far.

They were getting closer. Another ten metres, Porter thought. He could see Katie was using her fingers to try and claw her way to the surface, but she was so desperately weak it was hard for her to summon the strength to propel herself upwards. Hassad was reaching the surface now. He paused, then pulled himself free of the narrow tunnel. Turning round, he held out a strong hand, pulling Katie up, while Porter pushed her from behind, following swiftly in her wake.

They had emerged into a dark cavern that must have once formed a part of the main mine. It was so dark, Porter had no idea how big it was or where it led: the only light was the soft glow sneaking up the tunnel from the fires raging one level below them. ‘Where the hell are we?’ said Porter.

‘One level below the surface,’ said Hassad. ‘It’s a big mine, and we were using only a tiny part of it. These tunnels go on for miles.’ He nodded in front of him. ‘But to get out we have to go that way.’

Porter picked Katie up again and looked ahead. He could see nothing through the darkness. ‘How far?’

‘About seven hundred metres along this tunnel, there should be an old emergency exit that will take us up to the surface.’

‘You think it’s on fire?’

‘How the hell should I know?’ snapped Hassad.

Porter hoisted Katie onto his back. He was still wondering if Hassad was tricking him, maybe leading him straight into a troop of Hezbollah fighters on the surface. I’ll fight that battle when I get to it, he told himself. ‘Then we better get moving.’