Sorry can you specify about the thank you letter Ducarouge wrote to Senna?
sure can! it's from this text by johnny rives, i'm just gonna quickly translate the extract because i kind of want it on my blog:
I think [Senna] trusted me quite a lot. He proved it to me in a rather moving manner at the end of 1987, after he had signed with McLaren. It was in the evening, after the last practice session of the Australian Grand Prix, the last race of the season. I was wandering through the paddock when he saw me and made a sign for me to join him. He was sitting near the Lotus garage where the mechanics were busy preparing the next day's race. "I need to show you something," he told me. I sat next to him and he produced a letter from his pocket. "There, read it, but don't talk about it in your newspaper...". This letter had been written to him by Gérard Ducarouge who, as Lotus's technical director, had just experienced three unforgettable seasons with Senna. In it, Gérard talked about the pride and gratitude he deeply felt towards him. It was a beautiful letter, imbued with deep, genuine emotion, which I could summarize in this way: "I feel very proud of having worked alongside you these three seasons. You are the most fascinating, motivating and brilliant driver I have ever worked with. I will never forget the professionnal moments we have shared, they are the most beautiful of my whole career." Sadly, I can't perfectly retell from memory alone the emotions that Gérard Ducarouge had managed to express in this superb missive. Emotions that Senna had perceived to the fullest as I discovered very quickly since, when I handed him back the letter after having read it, I realized that he was in tears. It was of course a very intense moment between him and me, and which sealed our bond.