LONDON, England -McLaren team boss Ron Dennis still struggles to speak about the special bond he and the Formula 1 great shared, even 20 years after his death.Dennis, whose McLaren cars took Senna to three Formula 1 World titles, rarely delves publicly into his memories of a man who "was so good for the whole time he was on the planet."Senna's death left Dennis devastated; the McLaren boss still regards it as a private and complex affair, preferring to keep his emotions to himself, but as the 20th anniversary of Senna's passing is observed at the Imola track Dennis remembered one of the most fruitful collaborations in the history of the sport...ARGUED OVER A HALF-MILLIONDennis signed Senna with McLaren in 1987 on a day he will never forget. As negotiations neared conclusion, Senna and the McLaren boss could not agree on the money.Dennis said: "We were arguing over half a million dollars, and I came up with the idea of us flicking a coin to decide. But Ayrton's English wasn't so good at the time, so there was a five-minute conversation about the details."That episode spoke volumes about Dennis and Senna's playful mindsets. It also marked the beginning of a five-year relationship, sometimes marred by feuds and disagreements, but mostly made of joy. During his time at McLaren, Senna triumphed in 35 grands prix races.Dennis said: "He gave me an envelope once, I still have it at home The envelope's been opened, but when he gave it to me it had the equivalent of R100 000 in it, the result of a bet we made that I could not eat a container of chili in Mexico." Dennis said one of the reasons many people consider Senna to be the greatest ever is because he died too early.RUTHLESS ON TRACKOn the track, Senna was ruthless as can be and infuriated many of his rivals, including French nemesis Alain Prost. Senna and Prost spent two years at McLaren together in 1988-89 and Dennis was there to witness first-hand their long-lasting feud. At Imola in 1989, Prost accused Senna of breaking a pre-race agreement but Dennis said both drivers were to blame.Dennis said: "They broke each other's confidence. They both made commitments to each other several times that was one that came into the public domain. There was tremendous tension and anger ... Those two were perfectly matched in deviousness."The dispute reached its climax the year after at the penultimate race of in Japan, when Senna crashed into the Frenchman at the first turn, guaranteeing himself his second world title. The move disappointed Dennis.Dennis said: "I remember looking at all the traces - the brake and throttle pedal -and you didn't need to be Einstein to work out what happened. When he came back to the garage, I told him I was disappointed in him. He got it. He didn't have to say any more. I don't think he was particularly proud of what happened."But according to Dennis, that was just a moment of weakness in an otherwise flawless career.Stay with Wheels24 for the 2014 F1 season – fresh reports every day.