I T was the weekend when everything changed in Formula One, a two-day period where a brace of contrasting characters perished at the treacherous Imola circuit 20 years ago.
The first was a little-known but talented Austrian youngster, Roland Ratzenberger, who was killed during qualifying; the second was a Brazilian whose name had become as synonymous with F1 as his compatriot, Antonio Carlos Jobim, with bossa nova.
Nobody could quite believe it when Ayrton Senna was involved in a dreadful collision at Tamburello which propelled him and his car into a concrete wall.
Astonishingly, despite the sadness and despair which was etched on the faces of those who attended to the stricken driver, the San Marino Grand Prix was allowed to continue, even though it was obvious that one of the greatest competitors the sport had ever known had suffered mortal wounds.
There was no champagne sprayed on the podium afterwards, but as Britain's Martin Brundle said: "I was angry that we carried on racing. I'm still angry today, if I'm being honest.
"We raced past a pool of his blood for 55 laps. I thought that was disrespectful and simply not the right thing to do."
Eventually, more than four hours after the incident, came the news which everybody had dreaded and which cast a veil of tears over the world of sport. Senna, gifted, mercurial, a hero in his homeland and throughout the globe, but also a mass of contradictions was dead at the age of just 34. It was a seismic event, which raised as many questions as answers. In the long term, it highlighted the whole question of safety in the pit and paddock. Yet few were concerned with that in the next few days.
That whole Imola meeting resembled a bad dream for many of the participants. On the Friday before the main event, Rubens Barrichello, Senna's young protege, crashed heavily and missed the GP. Within 24 hours, Ratzenberger's car span out of control at 195mph and became airborne before colliding with a wall and finishing on the inside of the Villeneuve curve.
Soon enough, it emerged he had not survived and Senna's agitation was palpable. His friend, the long-serving neurosurgeon Dr Sid Watkins, advised him to withdraw from the race, so the pair of them could go fishing.
But, despite Senna's anxieties over the state of the circuit and his grief at the demise of a colleague, he could not bring himself to follow Watkins' suggestion. It was in his blood to push himself to the nth degree and recover from adversity and, oblivious to the evidence that he was not quite the force of old, he was determined to stem the charge of the new kid on the block, Michael Schumacher. It was a fatal decision on his part, rendered more poignant by the fact that he and his former rival, Alain Prost, arranged a meeting on the Sunday morning, where Senna lobbied the Frenchman for support for improved safety.
The two men agreed to join forces at the next race on the calendar in Monaco. It was one date which was never kept.
Murray Walker described Senna's death as "the blackest day for Grand Prix racing that I can remember". Tens of thousands of his fans stood in silent homage across Brazil and the build-up to his funeral was on a par with the passing of a pontiff or president.
But there were other, angrier responses from those who blamed such figures as Max Mosley and Bernie Ecclestone for increasing the risk element in F1 (to be fair, it should be pointed out that, until that weekend, nobody had been killed since 1982).
The Italian police launched their own painstaking investigation, while the FIA announced a series of new safety measures for Monaco, and the competitors reformed the GPDA.
In February 1995, a 500-page report was handed over to prosecutors, which suggested that a steering column had been the cause of Senna's demise. But, as with so many other aspects of the tragedy, this was hotly disputed and the legal arguments dragged on.
The only positive impact was that F1 is now probably safer than it has ever been and, whereas there has been regular loss of life in the last 20 years at Le Mans, in IndyCars, and (especially) in motorcycling, the last man to die in a F1 vehicle was Senna.
Nobody ever made a film called Clark. Or Stewart. Or even Fangio. But when Senna came out in 2010, everybody knew the subject matter and it was a resounding box-office triumph. It is a cliche to claim anybody is bigger than their sport, or it is in the majority of cases, but Senna was so much more than just a multi-millionaire in the fast lane.
Even as he pocketed huge earnings, he invested much of it into the Ayrton Senna Institute in his homeland which continues to provide support and succour to tens of thousands of youngsters in Brazil.
The centre is now run by his sister Viviane and she once told me about the motivation behind the foundation; it was her brother's concerns about the disparity between his riches and the endemic poverty which plagued his country.
"He wanted to make a difference," she added. "And we have to keep working to make that happen."
It was a sign that, in many respects and regardless of his occasional tantrums and antics on the track, Senna was as close as we have come to witnessing a secular saint in a racing car.
LIFE AFTER SENNA
Torches get passed on all the time, but rarely in such an all-enveloping tristesse as that which surrounded the ascent of Schumacher to the role of the world's best driver.
For the next decade, the German dominated his opponents, amassed all manner of records and world titles and, outwith his own nation, was feted without being loved or even particularly liked. Part of this was his own fault: it grew as tiresome listening to his excuses after taking out rivals or attempting precipitate manoeuvres as it is tuning into a Jose Mourinho press conference. Senna at least admitted he could be wrong; Schumacher, on the other hand, turned hand-wringing into a specialist subject.
But now, he elicits sympathy without even realising it, as he lies in a coma following the serious injuries he sustained in a skiing accident last December. At 45, he is a classic case of somebody who could not replace the adrenaline rush and giddy exhilaration he gained from F1 with anything in a 'normal' existence, hence his ill-fated comeback, which ended with his reputation damaged. Would Senna have made the same mistake? We will never know, but one suspects that he would have flung himself into his foundation once he was no longer a champion on the track.
WHY SENNA STILL MATTERS
He was not a machine. Nothing he did could ever be confused with mediocrity. To some extent, you can spot traces of him in such different men as Roger Federer, Tiger Woods and Steve Redgrave. There is a sense that these individuals create their own standards and keep pushing for more, even if it means trying to beat the clock. Which, of course, is ultimately impossible. Senna once said: "Many times, I find myself in a comfortable position and I don't feel happy about it. So I have an enormous desire to go further and further, to travel beyond my own limits."
There are shades of Icarus in that remark. And nobody has ever forgotten him either.