Motor Racing: Williams apply spit and polish to restore lustre: World champions under pressure from rising force in Formula One as grand prix series begins its swing through Europe

The Formula One sages will tell you the season proper starts here, back on the Old Continent; that achievements in the early, distant skirmishes count for little in the heat of the European battle. Williams-Renault pray they are right.

Defeated twice by Michael Schumacher and Benetton-Ford, the defending champions know they must reassert themselves in Sunday's San Marino Grand Prix at the Autodromo Enzo e Dino Ferrari, or contemplate losing their crown.

This is a power circuit, where the Renault V10 bolted to the back of the FW Williams 16 ought to prove a potent weapon for Ayrton Senna and Damon Hill. The team have also been testing aerodynamic and suspension modifications.

Williams have been severely scarred by events so far. They have not won a grand prix since their last visit to Italy seven months ago. Three of the races since Monza have gone to Schumacher - described this week by Niki Lauda as 'the talent of the century' - the other two to Senna, driving for McLaren.

Despite claims to the contrary, Benetton's strength has surprised Williams. Nine days before the start of the season, I asked Bernard Dudot, the head of Renault's engine operations, if he was as confident about the team's championship prospects as he had been before the previous two campaigns. In response, he was concise: 'Yes.'

Benetton's relentless advance and the development of the Ford Cosworth Zetec-R engine do not explain it all. Williams have, by their own lofty standards, been sloppy.

Problems during practice in Brazil hindered Hill's preparations and lumbered him with a badly handling car in the race. At the Pacific Grand Prix, he retired with a transmission failure. The team had been alerted to a possible fault and failed to deal with it.

Hill's frustration was matched by Patrick Head's anger. The technical director bought Hill dinner that evening by way of a peace offering. 'We let you down,' he told the British driver.

Senna's spin in Brazil and first corner contretemps at Aida have presented the pre-season favourite with a challenge he cannot have feared. He has no points, Hill six, Schumacher 20.

Williams, renowned no-nonsense racers, will feel their backsides have been suitably booted. Hill tested their 'new bits' at Nogaro, in south-west France, early this week, defying the gloom and the locals by working through to 8.30 one evening after the rain relented. They figured the police offered less of a threat than Benetton.

'We have certain things which may help us go in the right direction,' Hill said. 'We can't afford to suffer any more beatings from Benetton. We've got to stop them or they'll build up too much momentum. It's time we put a stop to their progress and I think we will do that.

'What has happened has been a real spur in galvanizing the team to recover the position we held before. It hurts more when you lose it than when you've never had it. One of the dangers of being successful is that complacency can settle in. This is a sharp reminder that it's tough to stay at the top.'

The winner of this race in each of the previous three years has gone on to be champion and Senna, like his team-mate, is conscious that this is crunch time. 'We must not miss opportunities. If we do not take this opportunity, on a circuit which should be favourable to us, it will be hard to recover the points,' he said.

At the age of 25, Schumacher has, according to Lauda, 'climbed the ladder quicker than Senna and any of us'. Suddenly he is the bookie's choice for the title, a shift from Senna supported by history. The championship has only once been won by a driver who had nothing to show from the first two races. That was Jochen Rindt, in 1970.

Schumacher, however, remains guarded. 'I feel we cannot talk about the championship because it is still so early in the season and there is no doubt that Williams will get stronger. They are still developing the car, which was not ready for the start of the season as ours was,' he said.

'Many of the circuits from now on will favour the Williams car. We have all the power circuits to come, starting here. This is a circuit where Williams will be able to show their potential.'

This circuit should also suit Ferrari's V12 and, buoyed by a third and a second in the opening races, the faithful will doubtless be back on the hillside after virtually abandoning the cause last year.

Gerhard Berger, shouldering additional responsibility in the continued absence of the injured Jean Alesi, tempers the optimism. 'To fight with Michael and Williams is impossible for us at the moment,' the Austrian said. 'The results, though, give the team and the fans motivation. Imola should be better for us from the engine point of view and we are hoping testing will have given us a step forward.'