"Oh, aye. Well, best keep to the far side of the canal, then. Restricted area this side."

"Really? I didn't know there was Army land hereabouts."

"Aye, it starts about half a mile from here. As to whether it's Army, I wouldn't know. They don't tell me."

"Well, I suppose we don't need to know," Faber said.

"Aye. Drink up, then, and I'll see you through the lock. Thanks for letting me finish my tea."

They left the house, and Faber got into the boat and untied it. The gates behind him closed slowly, and then the keeper opened the sluices. The boat gradually sank with the level of the water in the lock, then the keeper opened the front gates.

Faber made sail and moved out. The lock-keeper waved.

He stopped again about four miles away and moored the boat to a stout tree on the bank. While he waited for night to fall he made a meal of tinned sausage meat, dry biscuits, and bottled water. He dressed in his black clothes, put into a shoulder bag his binoculars, camera, and copy of Rare Birds of East Anglia, pocketed his compass, and picked up his flashlight. He was ready.

He doused the hurricane lamp, locked the cabin door and jumped onto the bank. Consulting his compass by flashlight, he entered the belt of woodland along the canal.

He walked due south from his boat for about half a mile until he came to the fence. It was six feet high, chicken wire, with coiled barbed wire on top. He backtracked into the wood and climbed a tall tree.

There was scattered cloud above. The moon showed through fitfully. Beyond the fence was open land, a gentle rise. Faber had done this sort of thing before, at Biggin Hill, Aldershot, and a host of military areas all over southern England. There were two levels of security: a mobile patrol around the perimeter fence, and stationary sentries at the installations. Both, he felt, could be evaded by patience and caution.

Faber came down the tree and returned to the fence. He concealed himself behind a bush and settled down to wait.

He had to know when the mobile patrol passed this point. If they did not come until dawn he would simply return the following night. If he was lucky they would pass shortly. From the apparent size of the area under guard he guessed they would only make one complete tour of the fence each night.

He was lucky. Soon after ten o'clock he heard the tramp of feet, and three men marched by on the inside of the fence. Five minutes later Faber crossed the fence.

He walked due south; when all directions are equal, a straight line is best. He did not use his flashlight. He kept close to hedges and trees when he could, and avoided high ground where he might be silhouetted against a sudden flash of moonlight.

The sparse countryside was an abstract in black, grey, and silver. The ground underfoot was a little soggy, as if there might be marshes nearby. A fox ran across a field in front of him, as fast as a greyhound, as graceful as a cat.

It was 11:30 P.M. when he came across the first indications of military activity and very odd indications they were.

The moon came out and he saw, perhaps a quarter of a mile ahead, several rows of one-story buildings laid out with the unmistakable precision of an Army barracks. He dropped to the ground immediately, but he was already doubting the reality of what he apparently saw; for there were no lights and no noise.

He lay still for ten minutes, to give explanations a chance to emerge, but nothing happened except that a badger lumbered into view, saw him, and made off. Faber crawled forward.

As he got closer he realised that the barracks were not just unoccupied, but unfinished. Most of them were little more than a roof supported by cornerposts. Some had one wall.

A sudden sound stopped him: a man's laugh. He lay still and watched. A match flared briefly and died, leaving two glowing red spots in one of the unfinished huts. Guards.

Faber touched the stiletto in his sleeve, then began to crawl again, making for the side of the camp away from the sentries.

The half-built huts had no floors and no foundations. There were no construction vehicles around, no wheel-barrows, concrete mixers, shovels or piles of bricks. A mud track led away from the camp across the fields, but spring grass was growing in the ruts; it had not been used much lately.

It was as if someone had decided to billet 10,000 men here, then changed his mind a few weeks after building started.

Yet there was something about the place that did not quite fit that explanation.

Faber walked around softly, alert lest the sentries should take it into their heads to make a patrol. There was a group of military vehicles in the centre of the camp. They were old and rusting, and had been degutted: none had an engine or any interior components. But if one was going to cannibalise obsolete vehicles, why not take the shells for scrap? Those huts which did have a wall were on the outermost rows, and their walls faced out. It was like a film set, not a building site. Faber decided he had learned all he could from this place. He walked to the east edge of the camp, then dropped to his hands and knees and crawled away until he was out of sight behind a hedge. Half a mile further on, near the top of a rise, he looked back. Now it looked exactly like a barracks again.

The glimmer of an idea formed in his mind. He gave it time.

The land was still relatively flat, relieved only by gentle folds. There were patches of woodland and marshy scrub that Faber took advantage of. Once he had to detour around a lake, its surface a silver mirror under the moon. He heard the hoot of an owl, and looked in that direction to see a tumbledown barn in the distance. Five miles on he saw the airfield.

There were more planes here than he thought were possessed by the entire Royal Air Force. There were Pathfinders to drop flares, Lancasters and American B-17s for softening-up bombing, Hurricanes and Spitfires and Mosquitoes for reconnaissance and strafing; enough planes for an invasion.

Without exception their undercarriages had sunk into the soft earth and they were up to their bellies in mud. Once again there were no lights and no noise.

Faber followed the same procedure, crawling flat toward the planes until he located the guards. In the middle of the airfield was a small tent. The faint glow of a lamp shone through the canvas. Two men, perhaps three.

As Faber approached the planes they seemed to become flatter, as if they had all been squashed.

He reached the nearest and touched it in amazement. It was a piece of half-inch plywood, cut out in the outline of a Spitfire, painted with camouflage, and roped to the ground. Every other plane was the same. There were more than a thousand of them.

Faber got to his feet, watching the tent from the corner of his eye, ready to drop to the ground at the slightest sign of movement. He walked all around the phony airfield, looking at the phony fighters and bombers, connecting them with the movie-set barracks, reeling at the implications of what he had found.

He knew that if he continued to explore he would find more airfields like this, more half-built barracks. If he went to the Wash he would find a fleet of plywood destroyers and troop ships. It was a vast, meticulous, costly, outrageous trick.

Of course it could not possibly fool an onlooker for very long. But it was not designed to deceive observers on the ground. It was meant to be seen from the air.

Even a low-flying reconnaissance plane equipped with the latest cameras and fast film would come back with pictures that indisputably showed an enormous concentration of men and machines.

No wonder the general staff was anticipating an invasion east of the Seine.

There would be other elements to the deception, he guessed. The British would refer to FUSAG in signals, using codes they knew to be broken. There would be phony espionage reports channelled through the Spanish diplomatic bag to Hamburg. The possibilities were endless.