What did go wrong?

What was it that lost Nigel Mansell his sixth consecutive victory with only seven laps to go?

If Imola confirmed that Williams-Renault is still the dominant force in Grand Prix racing, Monaco served as a reminder of Ayrton Senna's sheer class and the old adage 'It's not over until the Fat Lady sings'.

As usual his McLaren was no match for the Williams-Renaults in qualifying, yet in a manner rendered unobtrusive by their sheer pace he was quick enough to carry the fight within reach of Patrese's to line up third on the grid he has dominated since 1987. And he was clever enough to pounce on the Italian right at the start. "I didn't want to pinch Nigel, so I was a little cautious,” admitted Riccardo. Senna expected that, in a nice piece of psychological warfare. He edged alongside, left his braking as late as he dared, and just managed to beat the second Williams without running into the back of the first as they filed through Ste Devote. That, in its way, won him the race. For while Mansell piled it on to pull out a 22s lead by half distance, Senna was ahead of the other major threat. Mansell had no buffer.

As the race went on, in fact, Patrese's handling got worse as he coped with fairly violent oversteer and a steadfast challenge from Michael Schumacher that began building from lap 22. But had he been ahead of Senna, the Brazilian would have been stymied just as the Benetton driver was. Senna knew this, of course, hence that big effort at the start.

Look at photographs of the Williams and the McLaren cornering, and the roll is as evident in the latter's comportment as it is absent from the former's. The active FW14B was blindingly quick in Mansell's hands as he and Patrese waged a shoot-out for pole position on Saturday afternoon. The Briton eventually won it with one of those supreme laps when he missed all the abundant traffic, and though Riccardo's effort was thwarted after an altercation with Bertrand Gachot which later almost led to blows in the pit lane, he was honest enough to admit that though he might have dipped beneath 1m 20s, he would not have bettered his team-mate's startling time.

If Riccardo struggled in the race, Mansell did not. From the green light he was gone, and there was nothing anyone else in the place could do about it. His fate, literally, was in his own hands.

In the past this year he has been criticised for continuing to pile on the pace, of setting fastest laps right up to the end despite the size of his lead. In Monaco, ironically, he did the opposite. That he was on a 'cruise' was underlined by the manner in which he almost casually stretched his lead by two full seconds just on lap 59, yet it would not be sufficient when the Great Drama unfolded on lap 71. Monaco has a notoriously slow pit lane entry, and by most reckonings you need 35s or more in hand if you need to come in without losing a place. When it all began to go wrong for Mansell that lap, he had only 30s on Senna, and eight of them had come on lap 60 when the Brazilian had had to come to a virtual halt at Mirabeau as Michele Alboreto recovered from a spin.

But why the pit stop? What did happen in the tunnel that lap when the car felt so unsettled?

Monaco being Monaco, there were some great suggestions. Mansell had decided on a little gamesmanship that backfired. He had been 'prevailed' upon to enliven the race for the television cameras (which in any case missed his stop on the live broadcast!). Somebody had shot at one of his tyres in the tunnel!

The man himself had this to say: "Coming through the tunnel I almost lost it and the back end just went down. I felt immediately that I had a puncture. The problem was that I was halfway from the pits so I had to drive so slowly that I lost 15s or so just getting there."

The more sensible suggestions appeared to be discounted one by one. He hadn't sustained a puncture. Goodyear spokesman Barry Griffin confirmed that the left rear tyre had been inflated when Mansell pulled into the pits. Mechanics dismissed thoughts that a wheel nut had worked loose. "And it wasn't a wheel bearing. Nigel would never have been able to run a lap in 1m 21.598s when he went out again if that had been the problem," said Patrick Head. "But something had caused interference between the wheel rim and the upright, and we found magnesium swarf from the wheel where something had machined it out."

A stone? Could such debris have momentarily become jammed, caused the wheel to snatch as it was expelled violently enough to machine away part of the rim, thus giving Mansell the impression that the rear end had dropped? After Patrese's Imola testing shunt, when a tyre had been punctured for half a lap but the active suspension had tended to disguise it from him, he could be forgiven for feeling cautious. Especially at unforgiving Monaco, especially as a new software package to detect such problems was not quite race ready.

Days after the event the theories changed again. "The wheel was loose," confirmed a spokesman. "Therefore the wheel nut must have been loose. That let the wheel rub against the brake caliper, hence the swarf we found. There is nothing on the telemetry to suggest a puncture. All the evidence points to a loose wheel nut, but it's unbelievable that it didn't come off."

"We are still processing the reasons why the nut came loose," said Head the following Thursday. "Since Hungary '87 we've gone to great lengths to avoid this sort of thing, and in all our racing and testing since then we've never had any indication of the problem. Corning in was exactly the right thing to do; otherwise he might have had a three-wheeler out on the circuit.

Mansell's recovery was dramatic. It had spectators who were desperate for excitement after an hour of having only Schumacher's chase of Patrese to cheer, jumping to their feet and crying themselves hoarse. But it was all pure theatre. In the cockpit of the McLaren Senna could see Mansell coming, could almost feel him slash away a second of his 5.1s advantage within one lap as the Williams' Goodyears reached temperature, and then all but three seconds next time round.

But he knew that all he really had to do was to keep his cool, keep on the line, and just avoid getting panicked into doing anything rash. That's tantamount to suggesting that he comb his hair in the morning, its so second nature to him. What made it easier was Mansell's tactics. "Whenever I expected him to challenge, he wasn't there," Senna told his engineers. "He always seemed to be in the wrong place at the wrong time "

"What did he think he was doing?" asked another driver. "Every time he weaved around behind Senna it might have looked dramatic, but all it did was coat his tyres with all the rubbish that was on the track, off the racing line. He should have dropped right back and then had a real run at Senna, kept on line and tried to push him into a mistake."

As it was, Senna turned off his rev limiter and kept his head, and though the Honda RA122E belched a violent cloud of oil smoke as he backed off at Ste Devote after crossing the finish line 0.215s to the good, victory was in the bag. He'd won his fourth consecutive Monaco GP against the odds, with luck and with sound judgement. And he had equalled the record for five wins and won the trophy named after the first man to achieve the feat, Graham Hill.

In his chase Mansell had been advised that he could use the richest mixture setting, P5, on the Renault RS3C, but he opted to stay with P3 since the unit was running perfectly. His problem was not one of revs, but simply that it was Senna who determined where he could put the power down as they accelerated in single file out of the stupid abortion of a corner that is Rascasse. In qualifying, or when ahead of other cars, the Williams' traction control worked beautifully there, but with Senna immediately in front. Mansell was thwarted.

That final flurry of excitement was much needed, for prior to that the 50th Monaco GP was pretty much a bust. Patrese clearly wasn't in a position to challenge Senna for second place, but good old Jean Alesi and Michael Schumacher provided some much needed entertainment in their scrap over fourth place. Just as he did with Prost in 1990 when he was driving for Tyrrell, Alesi caught Schumacher napping at Mirabeau on the first lap and dived through, but then the two of them had the inevitable tangle at the Loews hairpin on lap 12 as the German counter attacked. The Benetton nudged the Ferrari sideways, almost in slow motion, but both recovered as Berger, Brundle and Capelli, in line astern, all dutifully awaited the end of the pantomime. The incident had two effects; Schumacher damaged his B192's front wing and marginally took the edge off its handling, while Alesi's left-hand sidepod and electronics were damaged. Thereafter the Ferrari would refuse at times to respond to the commands Jean made of the gearbox, and on lap 21 Michael drove by in a nonetheless dramatic move as they wound their way between the tiers of Armco barrier going up the hill to Massenet. It's not an obvious place to try and it needs judgement and guts, especially since this was Schumacher's first race at Monaco, and he was running against one of the circuit's current aces.

Both had been electrifying in qualifying. Alesi in particular barely lifting even for a moment round the swimming pool section. Now, as Schumacher pulled away, to commence that chase of Patrese, Jean fell back steadily until his gearbox quit altogether in the chicane on lap 29. Up to that point, however, as all weekend, driver had outperformed car.

The same could not be said of Ivan Capelli. In a competitive car the Italian has always given a good account of himself as a racer, which makes his 1992 season to date so disappointing. In Italy there is constant media pressure against him, even nonsensical suggestions about his eyesight, but the fact is that he doesn't get on with the F92A. When Brundle got off-line and skated over the chicane on lap 19, pitting for a replacement nose and fresh Goodyears, the Briton delayed him further, but when Berger's engine blew on lap 33 the Ferrari gained another place. Capelli was running fifth by lap 60, steadily being caught by an electrified Brundle who was staging a remarkable recovery that had taken him past Comas, Suzuki, Lehto, Fittipaldi, Gachot and Alboreto and back into the points. That lap Ivan brushed a wall, bending a steering rod. On his next time round, the F92A spun lazily as he headed down to Rascasse, backing into the wall on the exit to the preceding left-hander and leaving him with more explaining to do. It is sad to see the steady decline of a charger.

For Brundle Monaco was an opportunity to rebuild his confidence further, and his times compared well with Schumacher's all through. Now what he needed to do was get back to his peak before the season slipped into its second half.

The final point went, and deservedly so, to Gachot, who drove well throughout and eventually won a weekend-long personal duel with the recharged Alboreto which had begun the moment prequalifying got underway on Thursday morning. Speaking of which, Roberto Moreno not only hauled the Andrea Moda Judd through that session, but qualified it for its first race. It ended with engine failure after only 11 full laps, but that was 11 more than you would have got odds on at the previous race.

As Ligier struggled to its 47th race out of the points, and Guy went back home to Magny Cours after being catcalled by his countrymen on Thursday, Lotus dragged itself from the depths with two excellent qualifying performances as Herbert and Hakkinen finally began to make progress with the new 107s. The Briton qualified ninth and was running there, on the tail of the Berger, Brundle, CapeIli dice for sixth, when increasing oversteer caught him out approaching Rascasse. The Finn was really flying, too. Mansell was the first into the 1m 25s, then Brundle on lap 11, followed by Hakkinen a lap later. Sadly, his pace slackened as he lost the clutch, and the gearbox surrendered to the extra strain on lap 30. Nevertheless, the team had indicated the 107's potential.

So, too, had McLaren the potential of the MP4/7A at last. In Imola the Williams drivers had reported that Honda had made progress on the power front, out-accelerating them from Tosa on a couple of occasions. Now, in Monaco, both reported again that the McLaren was pulling out a couple of lengths on them from Portier down to the chicane. Likewise, the red and white cars had good speeds across the finish line.

As he came round on his victory lap, Senna stopped by the McLaren pit to embrace elated brother Leonardo, before wheelspinning his way down the road for his fifth official meeting with Prince Rainier. As Mansell indulged in his usual post-race histrionics, near to 'collapse', and later let the tears flow in private, no doubt the World Champion was beginning to wonder after all what his chances were of staging a dramatic rearguard chase to retain his title for a third successive year. His was a lucky victory, but there were definite signs of progress for him to savour. Better still, from McLaren's point of view, the first chink in Williams-Renault's 1992 armour had become visible.

78 laps of 2.068 mile (3.327 km) circuit (161.298 miles; 259.538 km)

1st: Ayrton Senna – McLaren MP4/7A-Honda V12 – 1h 50m 59.372s
2nd: Nigel Mansell – Williams FW14B/Renault V10 – 1h 50m 59.587s
3rd: Riccardo Patrese – Williams FW14B-Renault V10 – 1h 51m 31.215s
4th: Michael Scumacher – Benneton B192-Ford HB V8 – 1h 51m 38.666s
5th: Martin Brundle – Benneton B192-Ford HB V8 – 1h 52m 20.719s
6th: Bertrand Gachot – Venturi LC92-Lamborghini V12 – 77 laps