So, on Thursday I have to be in Paris at 09:00 and will be finished by 17:00. Book a return ticket and off we go. Come Tuesday, I find out that we have an urgent meeting at the office in London and will not be able to leave for Paris until two hours later than originally planned.

This is where the simple return starts to be an issue. Of course, if you are travelling on a full economy or business class ticket, there is no issue. Otherwise, there is.

The way travel works, if you change the outward flight, you have to reprice the whole itinerary. This means that, though the return flight remains unchanged you may still have to pay an increased price for the return flight – and if the return flight is now full, save for a few full price seats that could cost.

The answer is to consider buying two one way tickets. Indeed, these can work out slightly cheaper than a return (or perhaps, slightly more). More importantly, if you change the outward flight, you will not have to re-price the return flight.