It is arguably the biggest dilemma facing business and leisure travellers alike – when should you book your flights to secure the cheapest rate?

Booking early often means you secure the best price but leave it too late and you risk paying a high premium in the last-minute scramble for seats.

But now a Japanese economist has claimed to have solved the problem – book exactly eight weeks in advance and make sure you book in the afternoon.

The eight-week result comes from work published in the latest edition of the Economic Journal in which Watanabe and his colleague, Marc Möller, have devised a complex mathematical equation to calculate the optimum booking time.

Their findings suggests that airline tickets are cheaper when purchased in the afternoons, rather than the mornings, as business travellers tend to book their tickets at work in the morning on the company account, whereas leisure travellers are more likely to book from home in the afternoon.

The economists write: “When we book our flight to London weeks ahead we have to account for the possibility of unforeseen events which make our trip to London impossible. In order to make consumers take their chances, airlines have to offer advance purchase discounts. As a consequence, ticket prices increase as the travel date approaches.”

Earlier studies appear to corroborate these claims, although there may be discrepancies between the pricing of long-haul and short-haul flights.

A 2004 study of flights from Nice airport showed that the average price of a flight increases by 12.7% within the last 22 days prior to departure.