IMOLA - Thousands of Formula One fans gathered for a commemoration on Thursday at the Imola circuit -- 20 years to the day after Brazilian champion Ayrton Senna was killed here in the sport's darkest day. Dozens of enthusiasts drove their own cars around the Enzo and Dino Ferrari circuit to mark the tragic anniversary of the 1994 San Marino Grand Prix. Ferrari drivers Fernando Alonso and Kimi Raikkonen were due to attend a ceremony later on Thursday for the man seen as one of the greatest drivers of all time. "Our hearts sank when they told us the news," said Marco, 31, Italian Formula One fan who was at Imola as a young boy on the day of the crash. Daniela, 39, from Belo Horizonte in Brazil said: "What moves me about Senna was his humility, his enormous charisma. He is in our hearts like family".-AFP