It is not the success, the domination or the three drivers' world championships and 35 races the Brazilian won over the six seasons they were together that the boss singles out. It is, quite simply, "the fun".





"I remember the laughter and the fun," he reminisced to reporters at McLaren's Woking factory ahead of the 20th anniversary of the champion's death at the San Marino Grand Prix on May 1, 1994.





The increasingly extreme practical jokes played out between the serious-minded Senna, prank-loving Austrian team mate Gerhard Berger — who replaced Alain Prost in 1990 — and Dennis have gone down in Formula One legend.





There are the stories of Berger dropping Senna's supposedly indestructible carbon-fibre briefcase from a helicopter, of the Austrian filling the Brazilian's hotel room with frogs and replacing his passport photo with a picture of a penis.

Senna retaliated in his own fashion, glueing Berger's credit cards together and putting a whiffy French cheese in the air conditioning of his hotel room.

At Monza one year, Dennis returned to his plush hotel room at the five star Villa d'Este to discover it had been re-wallpapered with pornographic pictures.

"Needless to say, when one of the group got back to his room later that night there was nothing in it. Nothing. No furniture. No clothes. Nothing," smiled Dennis, still savouring the moment.





"I remember the laughter and the fun. Normally there'd be things verging on the slapstick and not so funny, especially damaging property which frequently happened... it was childlike but at the same time a really good feeling inside the team."





Senna had been in a dark mood heading into 1990 after a controversial Japanese Grand Prix in which Prost won the title after the Brazilian was disqualified in what he considered as a conspiracy by the French-run FIA.

He had decided to retire but returned to find a very different team mate.

"Gerhard gave me the perfect weapon to deal with Ayrton because he brought humour to the team," said Dennis. "I would say the concept of telling a joke and Ayrton laughing at it was not even possible before Gerhard got in the team.

"But then that just created a massive ice-breaker.



It got to the extreme. Gerhard has no limits. I mean, no limits.





He'll go to the point where it is positively dangerous.



There was one moment where we were up in Hamilton Island and were diving. And we were at quite a good depth and Gerhard just came and turned my air off. He thought that was hilarious."





On another occasion, on Dennis's birthday in Australia, they threw the boss off a yacht and then chucked in bait to see if they could attract sharks.





Senna was hard-headed about money, which he saw as both a measurement of his success and funding for his foundation in Brazil to help children in the favelas, and contract negotiations could be tortuous.





To break a deadlock over $500,000, he and Dennis once flipped a coin.



It was only afterwards that they realised the contract was multi-year and that toss had decided a cool $1.5 million.





Dennis said his fondest memory was when Senna handed him an envelope from his own personalised stationary with $10,000 stuffed inside.





The money was to settle a wager that the Brazilian had lost in Mexico over whether the principal dared to down an entire container of fiery chilli sauce.

"Before he could pull the bet back, I had wolfed it down. It was about the fourth time that he'd lost a bet, a big one, and I can remember him giving it (the money) to me and saying 'I am never going to bet with you ever again'," said Dennis.

"It's my fond memory for two things. To get a smile across Ayrton's face was not that easy. But to get him to part with his money with a smile on his face... it was a great moment. But I paid for it for a couple of days."





Senna won the championship in 1990 and 1991 with Berger as his team mate but with Williams in the ascendancy, and champions for the next two years, he made his move. He died in only his third race with that team, aged 34.

In the 20 years since, he has become a revered figure inside and outside the sport — held up as arguably the greatest driver of all time — and adored with almost religious intensity.





His funeral brought more than a million people — and some estimates say three times that number — on to the streets of Sao Paulo and the acclaimed documentary 'Senna' retold the story for a new generation when released in 2010.





The Brazilian had his failings, although those close to him say it was more absolute self-belief than arrogance, which were most evident in the notorious duels and collisions with Prost.





He was a wily tactician, politically astute but also possessed of huge charisma, charm and deep spirituality. Dennis understood why his former driver and friend remained so adored.



"He was so good for all the period he was on the planet. I can see no positiveness in





"I think there's lots of drivers that stay in the sport too long. And they tarnish their greatness. He was just unbelievably competitive and then boom! Not there.

"So what do you remember? I never thought 'I wonder what Ayrton would look like if he were here today?'.





Well, one thing he would look is a hell of a lot older.



And he would have had other things in his life that would have detracted from that reputation. He might have had a failed marriage.





"He just came to an abrupt end so you remember that greatness. That's one thing. And secondly he was great. Because he had human values, he was very principled."

Dennis was on the McLaren pit wall when Senna crashed in the San Marino Grand Prix, his third race for Williams. At that point, the man who had been one of those closest to the Brazilian took the decision to 'close down' emotionally.





"Some of the things in the 'Senna' film, the people that talk... I would say these guys know nothing," he declared.





The Senna he knew, with his mastery of Monaco and brilliance in the wet, was "so awesome that it was hard to distinguish one bit of awesome from another. He was a great guy."





Reuters A brief timeline of the weekend at the 1994 San Marino Grand Prix that claimed the lives of Ayrton Senna and Roland Ratzenberger:



The race was the third round of the year.



Triple champion Senna had started on pole position in Brazil and in Japan but had yet to score any points while Benetton's young German Michael Schumacher, in his third full season, had won the first two races.





April 29: In qualifying practice for the race, young Brazilian Rubens Barrichello - in his second season with Jordan - hit a kerb and the car took off at the Variante Bassa, hitting the top of the tyre barrier before coming to rest upside down.



Barrichello was knocked unconscious and taken to hospital. He suffered a broken nose and was ruled out of the race.





"By the time the helicopter took off to take Rubens to hospital we were all fairly confident that he was going to be all right. Spirits were high, congratulations to the medical team were welcomed.



The system had worked and the result was joyful." — The late F1 medical delegate Sid Watkins, a close friend of Senna's, wrote in his 1996 book 'Life at the Limit'.





April 30: Final qualifying on the Saturday before the race. Austrian rookie Ratzenberger lost control of his Simtek and hit a concrete wall head-on at the Villeneuve kink.





He had damaged his front wing on a kerb on the previous lap, which then apparently failed at around 300kph.

n Senna, who had been to the scene of accident, turned up at the medical centre and was devastated. It was the first driver fatality in F1 in nearly 12 years.



"Ayrton was beside himself: He had not been close to death at a circuit before... So many accidents in the past 12 years, so many serious injuries, but nobody irrevocably lost...Ayrton broke down and cried on my shoulder." - Watkins.





Watkins relates what he said to Senna after Ratzenberger's death: "Ayrton, why don't you withdraw from racing tomorrow? I don't think you should do it. In fact, why don't you give it up altogether? What else do you need to do?...give it up and let's go fishing."





The Brazilian replied: "There are certain things over which we have no control. I cannot quit. I have to go on."





May 1: Before the race, he had made peace with old, and by then retired, rival Alain Prost.



"I miss you," Senna told him. The Brazilian then lined up on pole for the third race in a row, with Schumacher alongside.

Finnish driver JJ Lehto stalled his Benetton on the grid.



Those behind him managed to avoid the car but Portugal's Pedro Lamy, unsighted, ploughed into the back of it. Neither driver was hurt but nine people were injured by debris.

n The safety car, reintroduced into F1 the previous year, came out for five laps which reduced tyre temperatures and the race then resumed with Senna leading.

n On the second lap after the re-start, Senna's Williams speared off at Tamburello and hit a concrete wall. The race was stopped immediately and cars returned to the pit lane. Senna was extracted from the car and flown to hospital.



Thirty seven minutes after the crash, the race re-started and was won by Schumacher. No champagne was sprayed.





At 6.40 pm Italian time, nearly two and a half hours later, it was announced that Senna had died.





n Austrian Niki Lauda summed up the grim weekend: "God has had his hand over Formula One for a long time. This weekend, he took it away."

Ask Ron Dennis what he misses most from the time when Ayrton Senna was driving for his McLaren Formula One team and the answer may come as a surprise.