"That's a fond memory because getting a smile across Ayrton's face was not easy, but getting him to part with money was even more difficult!"
Dennis said one of the reasons many people consider Senna to be the greatest ever is because he died too early.
"I can see no positives from the fact that he had an accident and lost his life, but it means that you didn't see his decline," Dennis said. "There are lots of drivers that stay in the sport too long and tarnish their greatness."
On 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.