Database: olympics
Question: In which year did London hold its earliest Olympic game?
SQL: SELECT T3.games_year FROM games_city AS T1 INNER JOIN city AS T2 ON T1.city_id = T2.id INNER JOIN games AS T3 ON T1.games_id = T3.id WHERE T2.city_name = 'London' ORDER BY T3.games_year LIMIT 1