'Why didn't he go back?' said Max as the path widened and Bernard came up alongside him.

'Who?'

'The poacher. Why didn't he go back and look at his snares?'

'You mean we are already in the Sperrzone? There was no fence, no signs.'

'Locals know where it is,' said Max. 'Strangers blunder onwards.' He unbuttoned his coat and touched the gun. There was no practical reason for doing so except that Max wanted to make it clear to Bernard that he hadn't come all this way in order to turn himself in to the first person who challenged them. Max had shot his way out of trouble before: twice. Some people said those two remarkable instances of good luck had given him a false idea of what could be done when facing capture; Max thought the British with whom he worked were too damned ready to let their people put their hands up.

He stopped for a moment to look at the lake again. It would be so much easier and quicker to be walking along the valley instead of along this high path. But there would be villages and farms and dogs that barked down there. These high paths were less likely to have such dangers but the ice on the northern aspects meant they were sometimes slower going and the two men didn't have time to spare.

The next hill was higher and after that the path would descend to cross the Besen valley. Perhaps it would be better to cross it somewhere else. If the local police were alerted they were sure to put a man at the stone bridge where the footpath met the valley road. He looked at the summit of the hill on the far side of the river. They'd never do it. The local people called these hills 'mountains', as people do in regions where no mountains exist. Well, he was beginning to understand why. After you walked these hills they became mountains. Everything was relative: the older he got the more mountainous the world became.

'We'll try to get over the Besen at that wide place where the stones are,' said Max.

Bernard grunted unenthusiastically. If they'd had more time Max would have made it into more of a discussion. He would have let Bernard feel he'd had a say in the decisions, but there was no time for such niceties.

Scrambling down through the dead bracken and the loose stones caused both men to lose their balance now and again. Once Max slid so far he almost fell. He knocked his wounded arm when recovering himself, and the pain was so great that he gave a little whimper. Bernard helped him up. Max said nothing. He didn't say thanks, there was no energy to spare.

Max had chosen this place with care. Everywhere on its east side the Wall occupied a wide band of communist territory. Even to get within five kilometres of the Wall itself required a permit. This well guarded and constantly patrolled prohibited region, or Sperrzone, was cleared of trees and any shrubs or growth that could conceal a man or child. Any agricultural work permitted in the Sperrzone was done only in daylight and under the constant surveillance of the guards in their watchtowers. Artfully the towers were different in height and design, varying from the lower 'observation bunkers' to the tall modernistic concrete constructions that resembled airport control towers.

But in the Sperrzone of that section of the frontier that NATO codenames 'piecemeal', good or bad fortune has called upon the DDR to contend with the lake. It was the presence of a lake at a part of the Wall that was undergoing extensive repair work that caught Max Busby's attention in the so-called Secret Room.

For the regime it was a difficult section: the Elbe and the little river Besen that feeds into it, plus the effect of the Mause See, all contributed to the marshiness of the flat land. The Wall was always giving them problems here no matter what they did about waterproofing the foundations. Now a stretch almost three kilometres long was under repair at seven different places. It must be bad or they would have waited until summer.

Getting through the Sperrzone was only the beginning. The real frontier was marked by a tall fence, too flimsy to climb but rigged with alarms, flares and automatic guns. After that came the Schutzstreifen, the security strip, about five hundred metres deep, where attack-trained dogs on Hundelaufleine ran between the minefields. Then came the concrete ditches, followed by an eight-metre strip of dense barbed wire and a variety of devices arranged differently from sector to sector to provide surprises for the newcomer.

To what extent this bizarre playground had been dismantled for the benefit of the repair gangs, remained to be discovered. It was difficult to forget the helicopter. The whole military region would be alerted now. It wouldn't be hard to guess where the fugitives were heading.

When they reached the lake it was not anything like the obstruction that either of them had anticipated. They'd been soaked to the knees wading across the slow-moving Besen. The necessary excursion into the Mause See – to get around the red marker-buoys which Max thought might mark underwater obstacles – did no more than repeat the.soaking up to the waist. But there was a difference: the hard muscular legs had been brought back to tingling life by brisk walking, but the icy cold water of the lake up to his waist drained from Max some measure of his resolution. His arm hurt, his guts hurt and the arctic water pierced through his belly like cold steel.

The snow began with just a few flakes spinning down from nowhere and then became a steady fall 'What a beautiful sight,' said Bernard and Max grunted his agreement.

There was just a faint tinge of light in the eastern sky as they cut through the first wire fence. 'Just go!' said Max, his teeth chattering. 'There's no time for all the training school tricks. Screw the alarms, just cut!'

Bernard handled the big bolt-cutters quickly and expertly. The only noise they heard for the first few minutes was the clang of the cut wire. But after that the dogs began to bark.

Frank Harrington, the SIS Berlin 'resident', would not normally have been at the reception point in the Bundesrepublik waiting, in the most lonely hours of the night, for two agents breaking through the Wall, but this operation was special. And Frank had promised Bernard's father that he would look after him, a promise which Frank Harrington interpreted in the most solemn fashion.

He was in a small subterranean room under some four metres of concrete and lit by fluorescent blue lights, but Frank's vigil was not too onerous. Although such forward command bunkers were somewhat austere – it being NATO's assumption that the Warsaw Pact armies would roll over these border defences in the first hours of any undeclared war – it was warm and dry and he was sitting in a soft seat with a glass of decent whisky in his fist.

This was the commanding officer's private office, or at least it was assigned to that purpose in the event of a war emergency. Among Frank's companions were a corpulent young officer of the Bundesgrenzschutz – a force of West German riot police who guard airports, embassies and the border – and an elderly Englishman in a curious nautical uniform worn by the British Frontier Service, which acts as guides for ail British army patrols on land, air and river. The German was lolling against a radiator and the Englishman perched on the edge of a desk.

'How long before sun-up?' said Frank. He'd kept his tan trenchcoat on over his brown tweed suit. His shirt was khaki, his tie a faded sort of yellow. To the casual eye he might have been an army officer in uniform.

'An hour and eight minutes,' said the Englishman after consulting his watch. He didn't trust clocks, not even the synchronized and constantly monitored clocks in the control bunker.

Hunched in a chair in the corner – Melton overcoat over his Savile Row worsted – there was a fourth man, Bret Rensselaer. He'd come from London Central on a watching brief and he was taking it literally. Now he checked his watch. Bret had already committed the time of sunrise to memory; he wondered why Frank hadn't bothered to do so.