Good value or a waste of money? Liza Power dissects round-the-world fares.

Ten years ago round-the-world fares (RTWs) were more trouble than they were worth. They were expensive, restricted by limited flight paths, bad connections, days wasted in transit and inflexible ticket conditions.

But not any more. The formation of the three big airline alliances - Star Alliance, Oneworld and Skyteam - have revolutionised the way RTW tickets work. Here's a guide to RTW fares and how to make them work to your advantage.