By Andrew Benson
Ten years after Ayrton Senna's death, Formula One gathered at the San Marino Grand Prix this weekend to mourn his loss and consider his legacy.
Senna left a legacy that has outlived him
The ghosts of a decade ago were unavoidable at the Imola track, where Senna was killed when he lost control of his Williams at the Tamburello curve and smashed into a concrete wall in the San Marino GP on 1 May, 1994.
To some, it is a time for private grief. Team owner Frank Williams, in whose car Senna died in just his third race with the team, will be reflecting on personal pain and lost opportunities.
"I will keep my head low because it is a sad event," Williams says. "We don't want to be reminded of it too much, too overtly."
To others, it is a chance to remember a friend.
Ferrari driver Rubens Barrichello, to whom Senna was both a mentor and a hero, escaped his own horrendous accident that weekend. He describes his fellow countryman as "someone who was very special".
"In a way for me he has always been present," Barrichello adds. "It's not that I think about him every day, but being Brazilian and living the emotion of being a Brazilian, you live with Ayrton Senna every day."
And to Michael Schumacher, it is a time of many conflicting emotions.
Schumacher had a difficult relationship with Senna, who saw in the German an obvious threat to his rule of F1. And the German is fully aware that Senna believed him to be driving an illegal car in the early races of 1994.
Schumacher, Senna's successor as the best driver in the world, broke down in tears when he equalled Senna's record of 41 Grand Prix victories in 2000, and always finds himself at a loss for words when asked about Senna.
Barrichello's crash was the start of a harrowing weekend at Imola '94
But his memory of seeing his future rival do seemingly impossible things in a go-kart in 1980, when Schumacher was just 11 and Senna still four years from making his Grand Prix debut, is as vivid as the day it happened.
"That's the biggest recollection I have," Schumacher says. "It was something outstanding. For me, that was a very special moment, and I don't think it's necessary to speak about what he achieved afterwards - that is very obvious."
But it is not just F1 people who will be remembering Senna this weekend, for his death was felt across the world.
As with so many icons who die young, Senna's legacy has outlived him.
In Brazil, the charity he set up to help the nation's disadvantaged children is still going strong.
And F1 has never been the same since his death, something illustrated by Imola itself.
Changes made to the track have left it a shadow of its former greatness.
In 1994, Tamburello was a left-hand curve taken at more than 190mph; now it is an innocuous chicane - one of many on F1 circuits around the world.
Imola '94 was the first Grand Prix for 12 years at which a driver had been killed, and it came at a time when the sport was beginning to think it was so safe that fatalities had been consigned to history.
F1 was woken from that reverie with a start by a weekend of such horror that those who lived through it will never forget.
In three days, F1 was turned upside down.
First, Barrichello was knocked unconscious and swallowed his tongue when he crashed his Jordan with sickening violence in Friday practice.
His escape with only minor bruises seemed to underline how safe F1 had become, an illusion that was shattered forever when Austrian novice Roland Ratzenberger was killed instantly in a crash the following day.
Senna went to the scene of the accident - 200m further on from the point where he would lose his own life - and for several hours considered not racing the next day, even retiring for good.
But after a late-night talk with Frank Williams, Senna resolved to go on.
The sombre atmosphere turned blacker when a start-line crash sent a wheel bouncing into the crowd, injuring several spectators.
Ratzenberger was the first driver to be killed at a Grand Prix for 12 years
After six laps behind the safety car, the Grand Prix was restarted, and one lap after that came the crash that claimed the life of the man many believe to have been the greatest racing driver the world has ever seen.
The shockwaves reverberated around the globe.
In Brazil, where Senna had been a beacon of hope to struggling millions who felt their lives and country otherwise held little of which to be proud, there was anguish and shock, followed by days of national mourning.
In Europe, newspaper headlines demanded motor racing should be banned.
Italy began an investigation into the causes of the accident, a case that led to the acquittal of Williams' technical director Patrick Head and chief designer Adrian Newey, now at McLaren, on "culpable homicide" charges in 1999, but which still drags on today.
In F1, meanwhile, legislators began a series of rule changes aimed at making the cars safer.
That had happened in the past. The difference now was that it had become painfully clear that, whatever the inherent risks of the sport, the idea of a man dying in a Grand Prix car had become unacceptable to many of those who watched it.
Imola prompted a change in philosophy, and that quest for safety is pursued by the sport's governing body as aggressively now as it was in the dark days of 1994.
Senna had spent his final morning in meetings with fellow drivers, determined by Ratzenberger's accident to take on a new responsibility for driving through safety changes in F1.
Regardless of his powerful presence in the sport, it remains an open question whether he would have succeeded in life. The seismic impact of his loss meant there was never any doubt it would happen in his death.