Tonight Mastermind reaches the semi-final stage. Four of the early first-round winners compete in the imposing setting of the great transept of Lincoln Cathedral.Alistair Hanson (diamond valuator) The life and novels of Thomas HardyJohn Sutherland (retired civil servant) The life and times of John Paul Jones , 1747-1792 Jill McFatridge (area reporter) The 'Flashman' novels of George MacDonald FrazerIan Potts (railway signalman) The life and times of Alexander the Great