Question: The 1984 British Grand Prix was won by what driver who is the only one to have been a champion for both Ferrari and McLaren? 
Sentence (from "1984 British Grand Prix"): The 71-lap race was won by Niki Lauda in a McLaren-TAG, with local driver Derek Warwick second in a Renault and Ayrton Senna third in a Toleman-Hart.
Relevant evidence: Yes