They did the same with their last quiz,no one got them all so no winner.Last quiz the question I remember is 'film star' the answer was DD so I put Diana Dors,the answer was Doris Day
I think they are far more likely to sell their quizzes if there is always a winner. It is usual to give a prize to the person who submitted the nearest correct entry or, in the case of several entries with the same number of correct answers, to have a draw of these to determine a winner.