user: Question: What is Since, when Transfer Fee is "£ 12m"?
Columns: ['Nat.', 'Name', 'Since', 'Goals', 'Ends', 'Transfer fee']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['ESP', 'Almunia', '2004', 0.0, 'undisclosed', '£ 0.5m']
SQL:

assistant: SELECT "Since" FROM "Table" WHERE "Transfer fee" = '£ 12m';