That night they leaguered three-quarters of a mile before a track that wasn't properly a road but had been in use long before most other roads in the world. From the Mediterranean in the north it reached down some 1800 rambling miles through the real Sahara to Tamanrasset and finally Kano in Nigeria, and camel trains had been plodding it since Hannibal's day.

If the French had got this far, they had almost certainly used this track. But so would any Afrika Korps unit which had picked up the same rumour. They put a watcher at the trackside while the rest of them went on with the evening chores.

About half an hour before sunset, two aeroplanes flew northwards on the far side of the track. Through glasses, Tyler identified them as Stukas. They were flying suspiciously low and slow, although the nearest landing-ground was at least seventy miles away. De Carette felt a ripple of unease run through the patrol, and when the aircraft noise had faded, several of them quietly went around checking the camouflage nets and bushes piled on the vehicles.

"We shan't see them again today," Tyler said. "They don't have the night-flying lights and whatnot on the landing-grounds here. It's probably safer lighting a fire at night than by day. There must be dozens of Arab fires up and down the track." He gave a little chuckle, but went on frowning at the humps that were the Chevs. "Oh well… if you knows of a better 'ole, go to it."

Then he had to explain the old First War cartoon of the soldiers in a shell-hole to de Carette.

They kept watch on the track, in relays, until midnight. De Carette felt left out at not having been chosen, but the last watcher let him know why. It was a corporal called Bede, rather quiet and serious.

"Only a few camels," he reported. "But when it was clear I went down and took a shufti and there's been a lot of wheeled stuff recently. No tanks or half-tracks, just wheels. Some Opels and Volkses and some I don't know, Skip. I tried drawing a couple of them." He shone his torch on the signals pad and held it out – but to de Carette, not Tyler.

"I tell you," de Carette smiled, "I thought it was fantastic, quite absurd. How could I recognise the patterns of some old French tyres? I could not even tell you the patterns of my own cars or the jeep I had just been driving. But then I saw: all of them would know just that. Like their own signatures. I was ashamed and angry, but now I know they were telling me something. I might tell them about Africa, but they could tell me – the only professional soldier – about war. John knew it, of course."

He chuckled at the memory, coughed carefully, and said: "He asked Bede if he could tell which way they had been going, these tracks. But he could not. So John sent him back with his torch, a long useless walk, to have a look. It was his sort of discipline."

They renewed the watch again from before dawn. At half past nine, Tyler went off to take a stint himself. Without him, de Carette felt even less a part of the family, and suddenly very frightened. Here they were, behind enemy lines (insofar as that part of the desert had 'lines' at all) but they weren't dashing about, blazing away with machine-guns and watching fuel dumps go up in fountains of flame. They were crawling under the camouflage nets to tinker with the engines and guns, brewing up tea, smoking, re-reading tattered old letters from home, snoozing,… it was all so normal that it made the war seem very much more total than just the bombing of children and old women.

One of the Chev drivers, a lance-corporal known as Griff, came over with a blackened tea-can. "Cuppashay, sir?" He was a handsome boy from somewhere in London, his hair ink black except for the dust, and the lower half of his face looking as if he'd washed in ash. By now they all had four-day beards, ranging from the True Explorer to the Sadly Adolescent. Nobody shaved in LRDG; it was a waste of water but more than that a waste of hot water, which took fuel and time. What they heated, they drank asshay, though no Arab would accept Griff's brew as real tea.

"Thank you very much." De Carette offered him a cigarette.

"Ta, sir," Griff squatted down and puffed. "Is it true what they say about the Arabs around here, sir? I mean them not being like the Sennoos?"

"I am afraid that it is. Here, I think it would be a bad mistake to trust them."

"Yer." Griff frowned as he thought out the implications of this. In Libya, the Senussi were the LRDG's best allies against Italian overlords who shut them in concentration camps and, occasionally, took their chiefs up in an aeroplane and pushed them out without benefit of a parachute. But in Tunisia the French were the hated overlords, and de Carette had spent too long as a child in North Africa to have any illusions about it. Vichy had gained some popularity with its anti-semitic laws, but most popular of all – according to Intelligence – were the newly arrived German troops with their rigid good manners and open-handed payments for food and services rendered.

If 'liberation' meant a return to tight-wad French rule, most Tunisian Arabs wanted nothing to do with it.

"Yer," Griff decided. "Could make it tricky, that, sir. Mind, the Skipper speaks Arabic, did you know that?"

"He speaks it better than I myself do, and I was born in Algeria. He also speaks better French than I speak English."

"Yer." Griff nodded, satisfied. "He's dead clever, the Skipper. Wonder what he'll do, after the war? I s'pose he'll go to Oxford or Cambridge and be a professor. I can't see him wanting to be a bleedin' general."

It was a simple assumption, but Griff didn't live to see it come true. Ten minutes later, the aircraft found them.

The first was a lone CR 42, an old biplane fighter and just about the last of its type that the Italians dared fly over Africa. It droned along, weaving lazily, parallel to the track. The pilot was obviously searching the ground but whether he was looking for anything in particular… In any case, all they could do was lie still in the best cover they could find. Even if the vehicles hadn't been immobilised by camouflage, they couldn't have dodged among those hummocks.

The pilot could have seen something as small and chancy as the glint of a well-scrubbed cooking-tin; more likely it was the sheer bulk of the Chevs. They stood at least five feet high when loaded and even parked between the hummocks couldn't be made to look like small bushes. But whatever he saw, the moment was quite clear. The fighter stiffened out of its curving flight, then its engine howled as it climbed flamboyantly against the sun.

The patrol swore vividly and scuttled around, re-arranging themselves to meet the line of attack. They rammed magazines into the Tommy-guns and cocked them – and so did de Carette, although he hadn't much faith in pistol-calibre bullets bringing down an aeroplane. But there was no time to tear off the camouflage nets and get at the machine-guns on the vehicles, even if anybody had felt suicidal enough to try.

Fired simultaneously, four heavy machine-guns make a single stretched-out explosion: brrrrrap. The recoil checked the aeroplane for a moment in a sprinkle of falling brass cartridge cases, and dust erupted all around the wireless Chev. The Tommy-guns burped back. De Carette knelt up, the gun stabbing against his shoulder like a pneumatic drill.

The biplane climbed away, followed by the thin rattle of a single Lewis gun.

It was sheer chance that Bede had been working on the other Chev at the time. And it was probably his strict but unimaginative sense of what was right and proper that made him knock aside the bits of bush over the Lewis gun and pull down the netting until the barrel poked through. He might have run away from a Messerschmitt, which was a proper modern aeroplane, but not from some tatty old biplane.