I received a message that there was something wrong with the clutch. Alarm bells started to ring loudly in my head

It goes without saying that I had hoped to allow everyone to rest easy by bringing the championship to a climax in Portugal on Sunday. Instead, I finished second to my Rothmans Williams-Renault team-mate, Jacques Villeneuve and, between us, we made sure that the excitement will run right to the end of what has turned out to be a nail-biting 16-race season.

For the best part of the weekend, it seemed things were going my way. I beat Jacques to pole position by just nine-thousandths of a second during a highly dramatic qualifying session and then made full use of that by making a good start at an absolutely crucial time. Once again, Jean Alesi had made a blistering getaway but I managed to hold him back on the run to use first corner. Jacques, meanwhile, had been slow off the line and he was down in fourth place. All I had to do was drive cleanly and pull away while I had a clear track.

My gap to Jacques was a healthy 13 seconds until I came across two back markers who were having their own battle, trying to overtake each other and totally oblivious to everyone else. They were swerving all over the road so badly that it was impossible for me even to get close to them, never mind overtake. There was every chance that they would have knocked me off the road because they were not using their mirrors and had no idea I was there. That alone cost five seconds in one lap, a huge setback when you are working hard to gain every tenth of a second. There is little doubt that that loss would be very significant.

Meanwhile, Jacques had moved into second place and I was left in no doubt that he was going very quickly. He was really pushing hard in the knowledge that he had nothing to lose, but I knew it would be very difficult for Jacques to overtake. It was a case of keeping my cool, even though he had closed in and was right on my tail. I thought then I would find out how much of a margin he had left and I pushed really hard for a couple of laps and opened the gap. That was reassuring because I knew I had the ability to pull away. At that point, I was not unduly concerned. Provided I didn't make any mistakes, I was in good shape.

Just as I was about to make the last of three pit stops, I came across David Coulthard's McLaren limping along with a puncture. This happened on the way into the very fast corner leading on to the pit straight. You need to use all the road at that point and I found the McLaren on the edge of the track. I had to back off in order to avoid hitting him and that cost some vital time.

I made my pit stop and, just as it was about to finish, David came trundling down the pit lane in his wounded McLaren. Carl Gaden, our chief mechanic and the man with the "lollipop", had no option but to hold me at the very moment I needed to get going. Again, another second was lost. Jacques made his pit stop on the next lap and I was very surprised indeed when he came storming out of the pits and rejoined no more than 0.025sec in front of me. I knew in that moment that he had probably clinched victory.

I tried hard to stay with him and apply pressure but I wasn't able. He was too fast. And, of course, even if I could have given chase, I doubt whether I would have been able to overtake. After my disaster at Monza two weeks before, the right thing to do was think about the championship. Second place would keep the ball well in my court. So second would have to do.

Then even that suddenly became a luxury when I received a message that there was something wrong with the clutch.

Alarm bells started to ring loudly in my head. Under no circumstances could I afford to lose the six points for second place. Having my lead cut to nine points was one thing; seeing it dwindle to three would be quite another, I couldn't work out what the problem might be. All they told me was that I had to go to a different switch position which changes the clutch strategy in the gear change. As it transpires, I was actually quite lucky to finish the race.

I felt very disappointed, particularly for the British supporters who had travelled to Estoril in large numbers. The grandstand opposite the pits was full of fans who hooted their horns and waved flags each time I appeared in the garage. There was a fantastic turn-out all around the circuit and, sadly for them, I wasn't able to conclude the championship there and I presume they won't be able to go to Japan.

Although I only need to finish in the first six, I will tackle the race at Suzuka thinking only of what I need to do to win the championship, starting with qualifying ahead of everyone else and then control things from there. Believe me, I still want to win races and I hate the thought of finishing second-best. But I've got to think about the championship. I have waited a long time, so I can wait another three weeks.