user: Question: How many drivers had the fastest lap at Silverstone?
Columns: ['Rd.', 'Grand Prix', 'Date', 'Location', 'Pole Position', 'Fastest Lap', 'Winning Driver', 'Constructor', 'Report']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Brazilian Grand Prix', '26 March', 'Jacarepaguá', 'Ayrton Senna', 'Riccardo Patrese', 'Nigel Mansell', 'Ferrari', 'Report']
SQL:

assistant: SELECT COUNT("Fastest Lap") FROM "Table" WHERE "Location" = 'Silverstone';