Database: formula_1 (difficulty: simple)
Question: When was the last f1 season whereby Silverstone Circuit hosted the British Grand Prix?
SQL: SELECT T2.date FROM circuits AS T1 INNER JOIN races AS T2 ON T2.circuitID = T1.circuitId WHERE T1.name = 'Silverstone Circuit' AND T2.name = 'British Grand Prix' ORDER BY T2.year DESC LIMIT 1