In the first letter, written in May, he talks of the pair testing new water-cooled engines, with Senna clearly across all of the minute detail.
“Two water-cooled engines were tested,” he wrote. “They proved to be fantastic, running half a second faster than the same model with conventional cooling. These engines have a major advantage: they operate at an average temperature of 70Cs, while standard ones run at around 150C.
“The Englishman Fullerton did about ten laps (the first ten laps of the test), and then I began the real testing, comparing them with other standard engine models and, later on, with different tyre compounds.”
Senna illustrated this with a diagram showing the radiator, water pump, rubber tubing and drive belt, as well as a diagram of a piston, illustrating engine adjustments.
Senna included technical drawings alongside detailed descriptions
Christie’s Images Ltd. 2025
All doesn’t go smoothly, however, as described in the second letter from June, covering the Swiss race meeting and, before that, one in Jesolo, Italy, which Senna describes as “one of the worst races I have ever taken part in”.
The meeting brought tyre issues and a “major defect” with the carburettor, as well as regulatory issues with the water-cooled engines.
Even so, Senna can’t help but shine. In the first race, he collided with another kart while battling for fifth, dropped to the back of the field (of around 32 karts) but still finished 14th.
In the next race, he describes finishing behind race-winner Fullerton before more problems, this time with the chassis, hampers the final two races.
Despite competing in the World Karting Championship for five years between 1978 and 1982, Senna never did win the title, losing out to Fullerton in 1980 after the latter passed him on the final lap, which enraged the young Brazilian.
It was, Senna said, one of his greatest regrets.
The Senna letters and photographs are due to be auctioned on December 11 at the Christie’s Groundbreakers: icons of our time sale.