Ayrton Senna: The Black Weekend - Remembering the tragic weekend at Imola 20 years ago that saw the death of Senna and Roland Ratzenberger

The 20th anniversary of the Black Weekend sees the sport look back on Senna and Ratzenberger, the last two drivers to lose their lives in F1 behind the wheel

For 12 years the sport of Formula One had managed to avoid a fatality that previously had become all too commonplace.

And then came the 1994 San Marino Grand Prix weekend at Imola - three days that will forever go down as the blackest in F1's history.

Ahead of the 20th anniversary of Senna's death, here Ian Parkes looks back on the events of that fateful weekend:

Friday, April 29

Twenty years ago qualifying was held over two days, and it was in the first of the sessions on Friday the first serious accident occurred.

In his second season with Jordan, a 21-year-old Brazilian by the name of Rubens Barrichello, caught the kerb at the Variante Bassa, sending his car airborne, around three feet off the ground.

The Jordan then hit the top of a tyre barrier, with the force of the impact resulting in the loss of the front wing and both wheels on the right-hand side.

What was left of the car then barrel-rolled along the ground for 20 metres before resting at an acute angle on its right-hand side

Two marshals quickly righted the car, but it was apparent all was not well with Barrichello as he flopped inside the cockpit.

After being treated at the circuit medical centre, he was then taken to the nearby Maggiore hospital in Bologna, mercifully sustaining nothing more than a broken nose and a fractured arm.

As Damon Hill, then Senna's team-mate remarked at the time: "We all brushed ourselves off and carried on qualifying, reassured our cars were tough as tanks and we could be shaken but not hurt."

Saturday, April 30

Not since Riccardo Paletti at the Canadian Grand Prix of 1982 had a driver been killed over the course of a race weekend.

Twenty minutes into the final qualifying session, Roland Ratzenberger changed that statistic when he lost his life after slamming into a concrete wall.

In only his third grand prix of his debut campaign for Simtek, the 33-year-old Austrian had opted not to return to the pits after an excursion off track during which he damaged the front wing.

On the next lap, and after emerging out of the high-speed Villeneuve chicane on to a section of straight, the front wing became detached, rendering Ratzenberger a passenger as his car hurtled off the circuit at around 190mph.

The monocoque of the car, that had improved immeasurably in terms of its strength in previous years, remained relatively intact as it slid for almost 200 metres down the circuit before finally coming to rest.

Although attended to at the scene, and taken on to the Maggiore hospital, Ratzenberger died from his injuries, notably a fracture at the base of his skull.

Upon hearing the news, Senna broke down and cried, turning to close friend, the late Professor Sid Watkins, then the FIA's safety and medical delegate, for support.

Read more: Roland Ratzenberger remembered - Imola's forgotten tragedy
Senna's genius captured a generation that never had the privilege to see him
Dennis still struggles to speak about Senna

Sunday, May 1

At the start of the ill-fated race, JJ Lehto stalled from his fifth place on the grid in his Benetton, leaving him a sitting duck.

As the majority of the field flew past him, Lotus' Pedro Lamy ran into the back of the stationary Finn, spiralling off and into a wall.

Whilst neither driver was hurt, the hail of debris from the cars that had flown over the catch-fencing caused minor injuries to nine fans.

The incident resulted in the introduction of the safety car, which remained on track for four laps whilst the wreckage from the Lehto-Lamy crash was cleared.

At the head of the field having started from the 65th pole position of his career, on the second lap after the withdrawal of the safety car - and the seventh overall in the race - Senna was killed.

Senna's Williams left the track at the Tamburello curve at 190mph, travelling across the short run-off area and into a concrete wall, sustaining fatal head injuries.

Watkins, offering his reflections many years after the incident in the Senna documentary, said: "We got him out of the cockpit, got his helmet off and got an airway into him.

"I saw, from his neurological signs, that it was going to be a fatal head injury.

"Then he sighed and his body relaxed, and that was the moment - and I'm not religious - that I thought his spirit had departed."