They lowered Lecat over the wall and dropped down beside him. The vehicle lights were just coming out of the track onto the flat plain around the village. A scout car and a truck, which stopped well before the gate, obviously suspicious.

Yorkie simply lifted Lecat onto his back and started running. De Carette and Tyler snatched up all the rest and followed. They dodged behind the village and into the soft dunes. There they collapsed, panting.

After a few minutes there was a burst of firing, somebody shooting at a villager or just a ghost. Some shouting, then silence.

"Nobody's going to come looking for us in the dark," Tyler said. "Back around to the other jeep."

They had less than two hours to dawn and took most of it in helping Lecat through the tangle of hummocks and dunes. They had to bring him to the jeep, not vice versa; it was parked at what they believed was just out of hearing of the village – a long way on a desert night – they daren't bring it closer.

It was also parked rather carelessly, close to the track, because they had assumed they'd be back to it well before dawn. They were almost there when they heard it drive away.

For a moment, de Carette feared Tyler was thinking of a second attack on the village. But then they staggered back into the dunes, away from where the jeep had been parked because that would be the first place the Germans would come looking in daylight.

The day began with a pale light, like the first jet of a gas burner flaring across the stars. Streamers of red appeared overhead and then the bloodshot sun itself, bringing light but no warmth. They felt safe to light cigarettes and Tyler poured out one cup of water for each, in turn. They only had one cup with them.

"We're going to have to do some walking," he said.

"To Zella?" That must be 600 miles, more than the depth of France from the Channel to the Riviera.

"No. We'll head north."

"John, in the north is Rommel."

"We won't go that far. If we can get around west of the salt marsh, to Nefta, we'll find something. There was a rumour 1st Army had got as far as Tozeur, so they could be further by now. That's only about a hundred and twenty miles."

Instinctively, de Carette's mind began breaking the distance down into day's marches: rations, water, bivouac times… and it was all meaningless.

"John – we have soldat de la premiиre classe Lecat with us."

"Ask him if he'd rather surrender. It has to come from you."

De Carette turned reluctantly to the young soldier, very young indeed behind the patchy beard and pain-weary eyes. He already knew what the answer would be.

They began to walk. They walked very slowly, if possible along the troughs between the crescent dunes, which lay in roughly north-south lines and curved liked arches laid flat on the landscape. Sometimes they had to climb over a dune, where it was soft, deep and slippery, like wading through flour. The slightest breath of wind skimmed the sand off the crest of the dunes and drifted it into their eyes. Only Yorkie and Lecat has sand-goggles, but they were passed round in rotation.

Lecat always needed one man to help him along, since he'd abandoned the plank crutch when they first rescued him. Who needed a crutch to ride in the back of a jeep? One man carried most of the haversacks, a Tommy-gun and the water Jerry-can, which made him awkwardly lopsided like a heavy suitcase does. The third was resting from a bout with Lecat and just carried a gun, a haversack of grenades and a few odds and ends.

After two days they simply threw away the Tommy-guns, which weighed around twelve pounds, and the grenades which were a pound and a half each, leaving themselves with just two pistols. It-was ridiculous to pretend they might be a fighting force any longer.

Without Lecat, they could have marched over twenty miles a day. With him, they were managing five, at best seven. And just being forced to move so slowly was more tiring than a natural pace.

It was Yorkie who mentioned it first. "If t'Frenchie had been captured, Skip, ah reckon he'd be in t'ospitai by now, being fixed up fine. You do 'ear that Jerry runs good 'espitбis."

"He is a Frenchman," de Carette said coldly.

"He's one of us," Tyler said, that finished it. But Lecat wasn't really one of them. Armies are made up of tiny groups – platoons, patrols, squadrons, troops – with the fierce loyalty of shared experience and danger. Even to de Carette, Lecat was still outside the LRDG family.

They walked mostly by night and lay up by day. It was nothing to do with being seen: out in the sand, neither friend nor enemy would find them because nobody bothered to look. They were in a place that was impassable to vehicles, and in the desert war such a place was a nowhere. But the nights were too cold for sleeping without the greatcoats and tents they had lost with the jeeps, and the days often too hot to move far without sweating and getting thirsty. They usually found a bush and lay down in its thin shade, staying still even when they weren't sleeping, because movement wasted energy…

On the fifth night, they found the German airman. From his badges Tyler identified him as a pilot Oberfeldwebel; he must have parachuted or crash-landed somewhere in the Grand Erg, and then started walking with just his water bottle and maybe a few bars of chocolate. How long he'd been there, they couldn't even guess. Drifting sand had half buried him, but in that dry air there was no corruption. The face had mummified into something three thousand years old, rigid dry skin stretched back from the teeth. The teeth were clenched onto the stem of a dead bush.

They trudged on silently through the dunes that had an unearthly silvery beauty under the waxing moon. The landscape was so simple, so infinite, and there was no sound except the hiss of sand in the wind. They could be on another planet, where all that was asked of you was that you walk slowly through a silent black-and-silver loveliness for ever.

The sun spoiled it, coming up quickly and complicating their life with colour and heat and changes of wind, so that they had to hunt for a scrap of shade and dole out the small ration of water that was still cold after the night. The days were annoying, restless, unnecessary.

They were wearing out. They were dying.

"If one of us went ahead, Skip," Yorkie said, "like he could tell them where to find us. I mean the rest of us. I'd have to be one of those who stayed, I know. But…"

"You don't know," Tyler said wearily. "It's at least forty miles before we get out of this sand and go west for Nefta. That would be another four or five days supposing 1st Army's got that far. But even then they couldn't send a vehicle down here to pick you up. In any case, we're in enemy territory, give or take."

That day they hadn't found a bush, and were crouching in the lee of a crescent dune, carefully lighting one cigarette from another, and smoking them in rotation. Absurdly, they had fewer matches left than cigarettes.

"We walked into this," de Carette said, "so we must walk out of it."

"Lecat didn't walk out of it," Maxim said, after de Carette had been silent for half a minute. "Professor Tyler says in his book that his leg went bad and he died of that."

De Carette sipped his wine and, blinking as if he had just woken up, gazed around the cool-warm room that was not hot or cold, and at the bright sky and the snow peaks outside.

"It was not his wound, not that. He was a peasant boy, from l'Auvergne – so naturally they had sent him to Africa. Naturally." De Carette chuckled to himself, without humour. "That is the way of the Army. John and I talked to him, we learned about his widowed mother, his older sister who might become a religieuse, the work on the farm that he had been taken from… he talked enough. He was not dying from that leg. We shot him."