Test your mental agility with our giant Sudoku and you could win a stimulating Swish Sudoku Book. This stylish edition contains 100 puzzles that will keep you absorbed for hours. Send your solution to: Sudoku No.609, The Irish Mail on Sunday, PO Box 5332, Cardiff Lane, Dublin 2. Include your name and address. The winner of Super Sudoku No.608 is William Roche, Clonmel, Co. Tipperary.