In the command centre the air was quiet. The darkness seemed to press in. They were all watching the clock hands tick towards zero hour. When at last the hour struck, Bendikt said, ‘Are all our troops off?’

All eyes turned to Prassan. He nodded. ‘Yes, sir,’ he confirmed. ‘The last boat has departed Tyrok Beach. Withdrawal is complete.’

Bendikt let out a sigh. ‘Start the fuses,’ he commanded. ‘Holzhauer is about to learn the cost of victory.’

Prassan’s mouth was dry. In the days since Tor Kharybdis had fallen, the magazines under the Lone Redoubt had been stocked to the ceilings with explosives. All they needed to do was blow the island up and take half of Holzhauer’s Chasseurs with them.

The countdown began. When the moment came, Mere offered the detonation button to Bendikt. He made the sign of the aquila and then pressed it. There was no reaction.

Nothing.

Prassan felt his heart skip. The demolitions officer frowned and stepped forward as if to check the device, but as he did so he fell sideways as an enormous boom rolled out over the planet, and a plume of rock and debris lifted into the air, mushrooming up like a volcanic eruption.

Sheets of flame raced along the corridors of the Lone Redoubt as mega-tons of explosives caught fire and erupted. For those unfortunate enough to witness the event, it was as if the whole fortress had shrugged its shoulders and lifted hundreds of feet into the air. It was not just the Lone Redoubt. The whole volcanic cone of the island blew and then collapsed down upon itself, shattering into ruin.

The first initial explosion was followed by a number of further blasts that shook the ground and sent a gathering cloud of dust and smoke into the air. They ran around the island in a necklace of detonations, each one setting off further landslides. The volcanic plug that had long since held the elemental forces of the planet at bay was gone. Fountains of molten rock glittered yellow in the gloom of ash and destruction.

As the centre of the island collapsed, the sea rushed in, resulting in yet more explosions of superheated steam. Cliffs of black rock slid into the water, sending out a tsunami of boiling water in the direction of Crannog Mons. It smashed against Traitor Rock, where it curved around the island towards Tor Tartarus and the Imperial troops still fighting there.

The wave was half as high as the Leviathan Terra’s Contempt. The beast of war and her crew had no chance of escape. The wave swept it from the island.

But there was worse to come. Once the Leviathan had been torn free, the assault pipes buried within the causeway were exposed, and millions of gallons of boiling water rushed in to fill the void.

Thousands of Imperial Guardsmen were caught in the torrent. The lucky ones died instantly.