There was a crackling boom, like thunder heard from within a storm cloud, and the door exploded. Shards of metal and flame flew down the corridor. Before the smoke cleared Belgian guerrillas poured through the barricade, kicking aside the mangled girder. Among the Europeans were black faces.

Oberstgruppenführer Walter Hochburg felt a shudder of incredulity. Then the fury swelled in him, his black eyes glittering.

No nigger, no breathing nigger, had ever set foot in the Schädelplatz, his secret headquarters. He raised his rifle above the sandbags – it was a BK44, the one Himmler had awarded him – and lashed the trigger. Waffen-SS troops fired alongside him.

More guerrillas surged into the passageway.

‘Stand your ground,’ roared Hochburg. His voice was a raw baritone.

On either side of him, men were retreating to the next redoubt. Hochburg followed with a slack stride, certain of his own invincibility, his rifle searching out dark skin. He reached the second wall of sandbags and dipped behind them to reload.

‘Oberstgruppenführer!’

Before him was his new deputy, Gruppenführer Zelman: flat-faced, blond, unblinking. The buttons on his uniform were as untarnished as virgin silver. He had emerged from a side passage.

‘What news?’ asked Hochburg.

Zelman huddled low. ‘A thousand guerrillas, maybe more, including artillery. The main entrance and southern walls have been breached. We can’t hold out much longer.’

‘Where are my helicopters?’

‘You must leave, Oberstgruppenführer. Immediately. Your bodyguard are waiting to escort you to Stanleystadt.’ Stanleystadt: Kongo’s great northern city.

‘And have the blacks in our sanctum? Never.’ There shouldn’t be a single negroid within a thousand kilometres of the Schädelplatz. Hochburg slammed a fresh magazine into his BK44. ‘Get a rifle in your hand and fight. You, the auxiliary staff, kitchen porters, every last man.’

‘I didn’t come to Africa to die, Oberstgruppenführer.’

‘Then you have no right to be here.’

Not for the first time Hochburg regretted dismissing Kepplar, his former deputy. Whatever his failings, there was a man who would have relished defending the Schädelplatz. Zelman was a cousin of Heydrich’s wife and had been assigned to him after the invasion of Rhodesia faltered. To keep an eye on me, Hochburg told him the day he arrived.

A grenade landed between them.

Zelman grabbed Hochburg and yanked him into the side passage. The blast turned the entrance into a cascade of bricks.

‘I would have thrown it back,’ said Hochburg as he got to his feet, swiping away the dust. When the attack woke him he had put on his black dress uniform, the material straining against the brawn of his shoulders; now it was floured and torn.

Zelman led the way through the stone corridors of the Schädelplatz, till they turned into the main thoroughfare. He stopped abruptly.

Hochburg had been here fifteen minutes earlier, demanding the base at Kondolele get his gunships airborne. There should have been sentries by the door: instead only the smell of the wind. He pushed his deputy to one side and stepped into the command centre. The cloud-riddled dawn shone down on him, wands of orange and coral-pink light.

Hochburg felt a shifting inside himself. ‘It can’t be . . .’ he said. It sounded like his jackboots were treading on snails.

The command centre had taken a direct hit. In the middle of the room the table-map of central Africa was broken in two; above it, jigsaw pieces of sky. The black triangles that represented units of the Waffen-SS lay scattered on the floor. Hochburg stooped to pick one up, rolled it in his fingers as if it were a divining stone. Bodies were strewn on the floor, cables sparked. Only the telex machines seemed unaffected: they continued the merry chatter of war. By now he should have been the master of Northern Rhodesia, its copper mines serving the Reich, its cities and dusty plateaux cleansed of the negroid threat. His panzers had invaded the previous year and found British forces waiting for them. The swift victory he’d promised became a protracted retreat, the British eventually crossing the border and encircling Elisabethstadt, Kongo’s third city. A pendulum siege of attack and counter-attack had lasted ever since. With Hochburg’s army engaged in the south, the remnants of the Belgian Force Publique took advantage of the situation and launched a full-scale guerrilla war in the north. The Belgians, the previous rulers of Kongo, had been fighting an insurgency since the swastika was raised over the colony a decade earlier; now they were emboldened.

A female radio operator was beseeching her mouthpiece. Hochburg buried the black triangle in his pocket and placed his hand on her shoulder. Her hair was thick with dust, the right side of her face burnt. ‘Any word on the helicopters, Fräulein?’

‘We lost the line to Kondolele, Oberstgruppenführer.’

‘Reinforcements?’

‘Stanleystadt reports a new offensive started against the city an hour before dawn. They can’t spare any manpower.’

‘You must leave,’ said Zelman.

Hochburg scraped his palm over his bald scalp. ‘No.’

‘With respect, Oberstgruppenführer, if you’re captured, they’ll parade you in the streets of Lusaka—’

‘You think I care?’

‘Germania might, especially when you stand before a negro court.’

Hochburg sighed. ‘You would be more convincing, Zelman, if you weren’t so desperate to save yourself.’

‘You can’t command a counteroffensive from here. Stanleystadt is your better hope.’

‘This place is my home.’

‘There are no helicopters, not enough men. It’s already lost.’

The radio operator put up her hand to speak. ‘The Schädelplatz is more than the walls around us. It is an ideal. A beacon for our hearts.’ She was too shy to look at Hochburg. ‘As long as you survive, Oberstgruppenführer, so will it.’

‘The girl’s right,’ said Zelman. ‘We don’t have to die.’

Hochburg considered her words, unwilling to admit the truth. He patted her gently. ‘There’s nothing more you can do. Come with us, you’ll be safer.’

‘I shall stay, Herr Oberstgruppenführer. I’ll keep trying to reach the helicopters.’

‘You see, Zelman. Give me a battalion of girls and this war would already be won.’

He stormed from the room, his rifle held ready.

‘Where are you going?’ Zelman called after him.

Back in the passageways the lights flickered above Hochburg. There were sporadic snorts of gunfire, the shouts of Belgian guerrillas echoed along the walls. He was disappointed not to cross any as he made his way to his study.

The Leibwachen – his personal bodyguard – were waiting outside. He had dismissed them earlier as, goaded by Zelman, they fretted over his every move. All were dressed in dark combat fatigues with BK44 assault rifles. One held Fenris – his Rhodesian Ridgeback – on a leash. Hochburg cupped the dog’s face in his hands, inhaled his gamey breath.

The French windows of the study had been blown inwards, showering the floor with glass. A spectral smoke clung to the air. ‘Bring me some gasoline,’ said Hochburg, casting his eyes over the walls of books. ‘Then get down into the square and secure the area. Somebody carry the dog.’

He flopped down at his desk, unlocked a drawer and took out a piece of tightly bound sacking. Inside was a knife. There was a blink of silver as he withdrew it. This was the blade Burton had wanted to drive into his heart.

Burton Cole.

He was to blame for the death of Hochburg’s great love: Eleanor. Burton’s mother. She had chosen her son over him and in doing so condemned herself to a savage death. Hochburg would never forgive Burton. All these years on, his grief for Eleanor remained as raw as his need for retribution. His desire to watch her son burn – literally burn; to luxuriate in each crackling scream – quickened his blood more than ever. It was the itch of a phantom limb, beyond relief. Burton was dead: torpedoed and drowned off the coast of West Africa. Hochburg had issued the order himself. It was a decision he had come to lament.

As the war in Rhodesia spread back across the border to Kongo, he spent his nights imagining Burton’s final seconds. The boy’s panic as the ship began to list and fill with flames; the dilemma of surrendering himself to the fire or waves. A man would always throw himself overboard: the virulence of the human organism demanded it preserve itself, if only for a few minutes longer. Inevitably, Burton would breathe salt water: that was the moment Hochburg regretted.

He had been cheated of his final look into the boy’s eyes, its exchange of triumph and failure. Then Burton would descend into the darkness and oblivion, a release Hochburg had been denied. He knew who suffered the most: Hochburg lived with the pain of losing Eleanor every day.

A Leibwache entered carrying a canister that sloshed with fuel. Behind him Zelman stumbled into the room. ‘They’ve reached the command centre. We’ve only minutes to spare.’

‘What happened to the radio operator?’ asked Hochburg.

His deputy went to the portrait of the Führer and flicked the switch hidden in the frame, doing so with a familiarity that made Hochburg bristle. The painting swung open to reveal a secret chamber. In the ground was a trapdoor that led to an underground passage out of the Schädelplatz.

‘I’m not slinking out of here,’ said Hochburg, sheathing the knife.

‘Oberstgruppenführer,’ implored Zelman. ‘We must go now.’ His voice was sucked into the passage.

Hochburg turned to the Leibwache with the petrol. ‘The books,’ he said. It may have been too late to save the Schädelplatz but his enemies would not make spoils of his precious volumes. He supervised the dousing of his library, then ordered Zelman to burn them; striking the match himself would be too heartbreaking.

He stepped to the veranda. Below, the square was empty except for his men creating a perimeter. Streaks of light blazed on the hallowed ground as the bombardment continued overhead. There was one final object he had to save.

The most prized thing of all.