Each day’s trading is carefully scrutinised and compared to previous years, together with other variables such as where in the week Christmas Day actually falls.

In recent years, the addition of Black Friday promotions has added further complication and compounded the difficulty in forecasting.

However, this year I would propose a different and far simpler approach. Rather than having all the complexity of calculating numbers day by day, I would write a series of numbers on separate pieces of paper, put them in a hat, and ask the chief executive to pick one out. It is that unpredictable. Of course, this method has the added benefit for the finance director of making it the CEO’s forecast.