Why do relatives Down Under pay more than us for their air fares? A. Air fares from London are more competitive than from any other nation in Europe; it is the world capital of aviation, with far more people flying in and out than any other city on Earth. Competition is particularly intense to Australia. Even though there are no longer any direct flights to Perth, several top-quality airlines are after your custom. Qantas and its partner, Emirates, compete against Gulf rivals Etihad and Qatar Airways. All the top Asian carriers, such as Singapore Airlines, Malaysia Airlines and Cathay Pacific, are after you too. There are even exotic options such as Air Mauritius and South African Airways if you want to add an unusual stopover. As a result, prices are as low as they were a quarter-century ago, even though fares are subject to almost £100 in UK Air Passenger Duty. I am seeing quotes of £820 for a London-Perth return on Qantas/Emirate for travel in late January (a fabulous time to be in Perth, as you will know). Same dates, opposite direction: £1,000. Now, you may well be thinking: it is clearly equally competitive between Perth and London as it is between London and Perth. So why the discrepancy? Well, airlines like to charge as much as the market will bear. For most of the past 25 years, there has not been a huge difference between Australian and UK fares. But when the pound collapsed five years ago, the Australian dollar soared in strength. The Aussies seem content to pay the same sorts of fares in A$ terms in 2013 as they did in 2007 - about A$1,800 return from Perth to London. When expressed in sterling, today's price is about 25 per cent higher. If any of your Australian relatives make regular trips to the UK, it could be worth them buying a one-way ticket and then organising a suitable sequence of London-Perth-London tickets to take advantage of our good fortune.