Following Senna’s lethal crash early in the San Marino Grand Prix on May 1, 1994, F1 authorities legislated sweeping changes to make the cars and circuits safer. The urgent action was recognition that the previous 11 years with no driver being killed in an F1 race – and eight years since a fatality in testing – had been more good luck than good management.

Although the safety of the cars and tracks had improved in the 1980s following the campaign in the '70s to end the almost ritual slaughter of drivers every year, F1 was still unnecessarily dangerous early in the last decade of the 20th century. Drivers were vulnerable in their low-line cars and the tracks still contained too many hazards.

Senna was the last driver to die in an F1 race and the changes forced on the sport by his tragic demise have saved many lives since.

Progressively more stringent crash-testing procedures, constantly improved protection of the drivers in their safety-cell cockpits and the wholesale modification of the perilous parts of the circuits transformed the survivability of big crashes.

As a direct result of the safety reforms that followed Senna’s death, F1 has never gone so long without fatalities or serious injuries.

While his death was not entirely in vain, it is still raw in the memories of the millions worldwide, who witnessed it live on television – the first time a globally recognised figure was killed before an audience’s eyes.

Senna, then 34, was already a cult hero when he was taken so unexpectedly in an accident that had freak consequences. Although what caused his Williams car to spear off at the fast left-hand Tamburello corner at the Imola circuit on the seventh lap of the restarted San Marino GP has never been determined, his mortal injury was an unusual outcome.

When his car slammed into the concrete barrier beyond the corner, a right front suspension arm folded back and penetrated his helmet, piercing his brain.

Had the impact been at a slightly different angle, Senna would have climbed out, dusted himself off and expressed his disgust. Instead, F1’s darkest weekend ever claimed another life, following the death in qualifying the day before of well-liked Austrian F1 rookie Roland Ratzenberger, who was Australian David Brabham’s teammate in the struggling Simtek team.

Senna, who had switched from McLaren – with which he had won three world titles – to Williams, had failed to finish the first two races with his new team and was desperate to turn the tide at Imola. Williams was not the powerhouse he expected, having dominated in the previous two years, and he was pushing the team to overcome the shortcomings of his car.

So he was already anxious, and became increasingly concerned and distracted following his fellow Brazilian Rubens Barrichello’s narrow escape from a huge crash in practice on the Friday and then Ratzenberger’s death in qualifying on the Saturday.

Senna was not in a great frame of mind and there were suggestions at the time that he overcame a premonition of doom to start the race, for which he had won pole position from emerging upstart Michael Schumacher.

Such a feeling of foreboding would have been consistent with his deep spirituality. Although a ruthless racer, he was an emotional, deeply thoughtful, caring person out of the car.

Senna, whose fame in his native Brazil rivals soccer icon Pele, became more famous and revered in death, and his legend has grown to mythical proportions.

Debate rages among F1 aficionados as to whether he is F1’s greatest driver of all time and, for many, his sheer passion gives him the edge over fellow all-time greats Juan Manuel Fangio, Jim Clark and Schumacher.

Two leading figures in V8 Supercars have no doubts that Senna was the standout of F1’s golden era of the late 1980s and early '90s. Holden Racing Team managing director Adrian Burgess was a mechanic who worked on Senna’s cars at McLaren, and Tekno Autosport’s team principal Steve Hallam was his race engineer at Lotus in the mid-80s and also worked with him at McLaren.

''He was an incredibly special guy, very warm,'' Burgess recalled. ''He’s looked on now as a legend, but even then you knew you were working with an all-time great. You knew he’d go down in history as one of the best ever.''

Added Hallam: ''He was the best of his generation, simple as that. My principal memory of him outside of being the finest driver of his generation was that he was just a good human being. And I mean good in the very best sense of the word. He was a good person, very human, and he showed a lot of emotion.''

Burgess was also close to Ratzenberger, making Thursday’s commemoration and celebration of the 20th anniversary of Senna’s death – and the tragic events of that fateful weekend – even more poignant.

And Hallam has a tangible reminder of his privileged time working with Senna, who gave him one of his helmets when he left McLaren at the end of 1993. ''It’s a possession that I treasure immeasurably,'' Hallam said.

Senna was always popular in Australia, with which he has an historical bond, having scored his final F1 victory in the 1993 Adelaide GP. It was also his last appearance on a podium alongside his former arch-rival turned friend-at-the-end Alain Prost, with whom he fought F1’s most bitter feud in 1989 when they were warring teammates at McLaren.