He saw there was a low wooden wall only a few feet to his right, like a groyne. Men huddled behind it. He might get a bit of cover there, if he could reach it. He rolled towards the groyne, over and over, his pack bumping under his back. A stray bullet smacked into the shingle, only inches from his right eye, and a pebble splintered and peppered his face with a kind of shrapnel. He cried out, feeling the sting of blood.

But he got to the groyne. He pressed himself against the thick wood, which was dark and slippery with seaweed. It wasn't much protection, but it was better than nothing, better than being out there exposed on the shingle like a beached porpoise. The men already here were soaked, wild-eyed, some of them wounded. None of them was from his company.

He risked a look over the groyne. There was a pillbox directly ahead of him. He was right in its line of fire. He could not imagine the men inside it, fighting for their lives; it seemed like something superhuman, brooding, a slit-eyed monster spitting lead at him. Before it the beach was chaotic, cratered, men crawling or lying still, looking for cover in shell-holes or behind the wreckage of boats. He saw the black plumes of mortar fire, the crack of bullets, and toxic fumes and sprays of red-hot shrapnel rose up from shell falls. Overhead the aerial battle continued, much of it hidden by the murky low cloud. The RAF fighters dipped low enough to scour the men on the beach with their guns. And there were Luftwaffe planes in there too; he saw a Stuka dive bomber coming down to take on some English gun nest. There was a smell of cordite and salty sea spray and the rich, sickening tang of blood.

And there was a wall further up where more men crowded, seeking shelter, their soaked battledress dark. Ernst realised that he had joined one of the black lines he had seen from the sea: bands of black that were mortal men huddling behind whatever cover they could find, trying to stay alive.

It wasn't supposed to be like this, he reminded himself. Evidently the English resistance had been underestimated. A shot slapped the wood close to his face, and he ducked back down.

Well, he couldn't stay here. Looking around, he saw that others drawn up against the groyne had the same idea. One man, an unterfeldwebel, raised his arm.

Ernst moved with the rest. And for the first time since landing in England he raised his weapon and fired.

The troops advanced up the beach in turn. It was a long slog. It was a question of lift your head, take a shot to cover the rest, and then when they were firing take your chance to crawl a bit further forward, before ducking down again. Still the pillboxes fired. There were hazards on the beach too; Ernst nearly fell into a dugout improvised from a bit of drainpipe buried in the shingle, but the Englishman inside was already dead.

And then a mortar emplacement got its range, and the shells rained down on the beach all around Ernst. Men and bits of kit were thrown high in the air, men torn to pieces in an instant, their limbs scattered. Ernst found himself crawling desperately over the bodies of the fallen. You could even get a bit of cover, if you ducked down behind a corpse.

But gradually, he saw, inch by inch – life by life – the tide of the German offensive was rising up towards the defenders, and one after another their emplacements fell silent, put out of action by a rattle of gunfire or the pop of an explosion.

And as he climbed the beach, and the daylight gathered, he began to see the scale of the operation unfolding around him. To right and left, all along the four miles of this shallow beach as far as he could see, men were making their advance, fighting and dying, Twenty-sixth Division slowly achieving its objective. Back at the edge of the sea, beyond the litter of assault boats and splintered barges, more troop carriers were pressing to land, a great crowd of them still stuck off shore. But already the sapper companies were landing their heavier equipment. He saw mortars and machine guns being assembled, and a big PAK anti-tank gun, and even an anti-aircraft weapon. The first horses were landing, bucking nervously as they were led through the spray. There were even men struggling to drag the barges out to sea, so they could be towed back across the Channel to be loaded with the second wave.

When he reached the head of the beach, he had to crawl around anti-tank obstacles, big concrete cubes. And then he came to the barbed wire, already snipped and pulled back by the first wave of engineers.

At last he was almost under the face of that damn pillbox itself. It was sheer concrete that glistened as if still moist. A man rushed it, lobbed a grenade through that slit, and ducked down. The grenade detonated with a dull thud, smoke and fire billowed briefly from the slit, and the pillbox was silenced. Ernst cheered with the others, wishing he could have thrown the grenade himself.

And then one more push and he was on grass, the beach at last behind him.

He heard a throaty roar. He turned, lying on his back, breathing hard.

An amphibious tank was coming out of the water, its snorkel raised like an elephant's trunk, a monster rising from the deep. On a day of extraordinary sights, this schwimmpanzer was the most remarkable. But a wounded man, lying behind a heap of corpses for cover, was right in its tracks. He screamed and tried to crawl out of the way, wriggling. But the tank driver could not see him and he was crushed into the shingle. His guts were forced out of his mouth and his arse, like toothpaste from a tube.

Ben Kamen watched the landings from the look-out post, high on the walls at Pevensey Castle.

From horizon to horizon, as the sun rose, the beach was alight with the spark of firing. Shells came in from the sea too, where the German ships were firing on the coastal defences. There was even fire coming from big guns on the continent, massive rail-mounted Bruno-class, perhaps. And one by one the gun emplacements and Martello towers and anti-tank ditches and pillboxes that had been so hastily manned during the summer were silenced.

Ben glanced around the interior of the fort. He was at the west gate, a relic of the Roman fort. The Roman curtain wall surrounded a cluster of medieval buildings, a lesser fort within the mightier ruin. It was this vast expanse of enclosed space that had inspired William of Normandy to make his landing here, when he had made his own invasion; it had been a defensible place to land his troops that first crucial night nine hundred years back.

Well, the sea had receded since then. And now, after all this time, the fort had been adapted for another invasion, another war. The castle was host to a garrison that included Home Guard like Ben, and British and Canadian regular units. Pillboxes had been built into the ruins of the keep, and the towers of the inner bailey had been fitted out as a garrison. It was very odd for Ben to see the characteristic slit gun port of a modern pillbox cut into what was obviously medieval stonework, itself built of reused Roman masonry.

But it was the same all the way along the English coast. Martello towers had been pressed into service, more than seventy of them, hefty structures thrown up before the time of Napoleon when the British feared invasion by the French. Now, after a hundred and fifty years of patient watchfulness, many were falling silent after only hours of use.

'We're not going to stop this lot today, mate,' said Johnnie Cox. 'Not this way anyhow.' Johnnie was a Canadian.

Ben shrugged. 'Yeah, but that wasn't the point, was it?' He was aware of a faint Canadian inflection in his own voice; he had a habit of taking on the accents of others, in an unconscious strategy to fit in. 'This is the coastal crust; it's just supposed to slow them down. But when the counterattack comes-'