Most of the control was re-established but I still needed the whole width of the road before I could get the steering back to straight-path conditions and even when I'd managed it there'd be no useful future because they'd only line up another strike as soon as I was steady so I pulled the only trick in the bag, the one I'd saved for emergencies.

The odds were one in three.

Along this stretch the road was three cars wide. The strip in the middle of the two lanes was rough grass with flood-water gullies each side. At the moment I was doing the expected: trying to kill out the oblique lunges and bring her straight again. The dark shape was still in the mirror but less distinct: possibly they were holding back in case one of my tyres burst under the strain of the yawing action. They wanted me off the road: they didn't want me to start breaking up in front of them. Their great weight, moving at great speed, could ram an obstacle effectively but if the N.S.U. were wheels-up or sliding on its side the deceleration-figures could force them against the screen.

If I had been running straight I could have deliberately set up this swinging action but that would be unexpected and they would have been warned. There wouldn't be another chance like this — with the N.S.U. swinging expectedly from one side to the Other — unless they made a new strike and again failed with it I didn't want to rely on that because they were getting their hand in now and the coup de grace wouldn't be long in coming.

The whole operation depended on the mirror and on timing.

It was more difficult to do than I had thought. The little animal brain inside the back of my skull was snivelling about the risk. It would have liked the odds to be better than one in three.

Through the rhythmic series of swings the mirror went dark, light, dark, light as the N.S.U. crossed and recrossed the bows of the Mercedes and during the third or fourth light period I hit the brakes and felt the pull on the safety-harness as the speed came down and the tyres set up a long howling and I watched the mirror although there was no point in watching it because if it ever went dark again there'd be nothing else to do.

But it was all right. The 300 had been so close that it ripped metal off the side of the N.S.U. as its black shape came sliding past but the swing was already under control when the brakes had begun dragging and there was no more than a slight rolling on the springs. There was also one guaranteed factor in play: despite larger discs and tyres the Mercedes didn't have the stopping-power of the N.S.U. because of the difference in mass and this was so cheerful to think about that I threw in an added risk and cut the Lights and hoped that the near-blackout would worry them more than it worried me: the balance of life or death could depend in the final analysis on liver and carrots.

The howling noise went on and I freed the discs a couple of times to break down the friction as the needle swung through the nineties and below. Their lights came on and I saw the big silhouette still drawing away although it was under the brakes by now and slowing. Rubber-smoke began curling past my windscreen in little clouds and then I stopped thinking about the 300 and concentrated on what had to be done next. The side-lamps had been left burning so that the facia was lit and I could read the speed because after five kilometres at 180 k.p.h. my normal visual judgement would be affected and true speed through the lower register would seem slower than it was and I didn't want to roll her when I turned.

There was a strong smell of rubber and asbestos by now but the braking effect had damped out the last of the swings and we were on a perfectly straight course a metre from the grass centre strip and when the needle dipped below 30 k.p.h. I released the brakes and made a three-quarter-lock turn across the soft ground and into the faint light flooding from a car that was coming south on this track. I was already accelerating through the sixties and tucked well in but the driver had been worried to see me broadside on across the road even in the distance and he went by fast with a lot of noise from the horn because in any case it was strictly verboten to drive across the centre strip like that.

By the time the N.S.U. was over the ton and still climbing I began trying to assess the chances but the basic data was so vague that I gave it up. It would mean having-to work out how long it would take the Mercedes to slow up and how long it would take it to make the turn and close the gap again behind me on the north-south track. There had never been any question of foxing them: they would have got the rough idea the moment I braked, and the man who wasn't driving would have hung himself over the seat to see what I was doing. It was a question of using the only two advantages the N.S.U. had over the Mercedes on a straight run — acceleration and braking — and hoping to find some sort of peel-off point on this side before they closed up again.

I gave them something like three minutes.

There wasn't anywhere to turn off within that period and the obvious thing to go for was the loop-section where I'd taken on fuel. They would be big in the mirror before I could reach it but they might not succeed in knocking me off in tune. The idea had only one advantage: there weren't any alternatives. The N.S.U. would be faster along winding roads but there would be other traffic and there was the risk of smashing up an innocent family because the big 300 was in business now and no one was safe. The only hope was to stay on the autobahn and use the elbow-room.

Light began filling the N.S.U.

They had been quick.

There wouldn't be another chance of pulling the same trick again if I let them come right up on me so if there were anything to do it had to be done now and I thought of something and did it and the tyres shrilled again as the brakes came on at full grip. I judged the gap to be still big enough to make the operation worth trying.

The speed was down to 30 k.p.h. when I turned on to the grass centre strip and felt the rear end break away and corrected it and brought her back in the opposite direction with my undipped heads catching the Mercedes full across the screen. I could see them clearly, their hands going up to shield their eyes, the big car veering a degree in the glare and the brakes hissing on. Then it came at me.

I was ready for it but the grass was soft and I was late getting away because of the wheelspin and the glancing blow slung the N.S.U. full circle and for a while I was just sitting there looking along the headlight beams watching them start an initial slide along the centre strip that carried them sideways for fifty metres with turf ploughing up in a wave over the roof before the momentum died and their wheels began spinning again for grip.

I was back on the concrete before they were but the gap was only medium and they were closing as hard as they could and I knew that somewhere inside the correct black overcoats and stiff white collars the semblance of an emotion had been provoked. Anger. From my limited information I assumed that their controllers had given orders that I should be killed and that my death should appear accidental, but they were finding it more difficult than it had seemed and now they were angry because their pride I I was hurt. They were no longer implementing an arrangement: they were conducting a duel.

They wanted to kill me now. It hadn't mattered to them before.

This could make a difference. Emotion at very high speed could lead to misjudgement. But it was my sole consolation. The light was already a glare inside the car before the last of the mud was centrifuged from the tyres and we settled down on the top-limit mark with the windrush blotting out most of the engine sound.

Then they cut their lamps so that I couldn't see which side they were going for. The mirror was only a frame for vague movement now, dark and shifting and inconsistent.