‘How many have we killed?’ he barked.

‘Three, maybe four,’ said Steve. ‘But there must be more of the bastards.’

Porter walked towards the staircase. They could be certain there would be more Hezbollah fighters downstairs.

‘Stun grenades,’ muttered Steve.

Both men unhooked the oval devices from their ammo belts, pulled the cords, then tossed them down into the stairwell. There was a delay of three seconds, then the muffled sound of an explosion. The blast of the grenade unleashed a wave of heat, followed by a rolling cloud of gas that would temporarily disable anyone who encountered it. In the two minutes it bought them, the unit had to get their man.

‘Let’s go,’ shouted Steve.

Behind him, Porter could hear the sound of puking. At the side of the room, Collinson had just thrown up. He was leaning against the wall, looking down at his vomit in shame, clutching his chest as he tried to recover his breath. ‘You OK, mate?’ said Porter.

‘Bloody fine,’ snapped Collinson.

‘You don’t look it.’

‘I told you, I’m fucking OK,’ said Collinson.

‘You can stay here if you –’

‘Leave the fucking bed-wetter,’ shouted Steve. ‘We’re going down.’

Mike, Keith and Steve had already started to descend the staircase. Their boots were rattling across the bare concrete, sending a ripple of echoes resounding through the enclosed space. Porter followed swiftly in their wake. At the bottom of the stairs, there was a narrow corridor that stretched for twenty feet both left and right, with two doors in both directions. One man was lying unconscious on the floor, blood streaming from his nose: he had been knocked out by the smoke from the stun grenade. It was still filling the room with a noxious, brutal odour. A couple of pale light bulbs were filling the room with an eerie glow that struggled to break through though the fumes. With one swift movement, Steve emptied three rounds of ammunition into the skull of the man lying at his feet, shooting his brains out. The corpse twitched on the impact, and a chunk of broken skull bone skidded out across the concrete, but in less than a second the corpse had stopped moving.

‘Two men left, two right,’ shouted Steve.

His voice reverberated around the corridor, and was still ringing in Porter’s ears as he peeled right and started striding through the sealed concrete passageway. His M16 was cocked, as both he and Steve edged their way closer to the first doorway. They had already worked out the standard operating procedure back on the boat. Porter would kick the doors down, and Steve would stand behind him ready to shoot anything that moved. There was no need for either man to say anything.

From the corridor behind him, Porter could hear the rattle of gunfire, and then the sound of a man screaming. Without pausing to think, he held his rifle in his left hand, balanced himself, then threw his entire weight into the wooden doorway. As it flung open, Steve was already kneeling down at the entrance, his gun held in his arms. It took just a fraction of a second to establish there was no hostage inside, and the decision made, Steve loosed off a volley of fire. The bullets splattered around the ten-by-ten room, taking down the two guards who were still trying to recover from the fumes of the stun grenade. Neither man knew what had hit them: before they had time to reach for their own weapons, their lungs had been perforated with bullet wounds, sending both of them collapsing to the ground.