Why is the question so hard?

This is not a lottery or a free prize draw. It is a prize competition and the law says that to be in with a chance of winning, you must demonstrate your skill, knowledge, or judgement.

The law says that the question should be sufficiently difficult that a significant number of people either get the answer wrong or are put off entering. However, this means that the odds of winning are actually increased for those who get the answer correct.