Rescued in the nick of time

Hot-air balloonist Colin Prescot is planning to set a world record by flying 25 miles above the Earth. He explains why his watch just might save his life if things should go horribly wrong

Though the Breitling Emergency watch looks bulky, it's made out of titanium, which is a very lightweight metal and is light on the wrist. Dassault, the company that does aviation equipment, makes the transmitter. The watch's built-in emergency transmitter runs on the VHF frequency 121 decimal 5, which is the aviation emergency frequency for May Day calls. It only has one frequency, so it's always clear.

To activate the watch is quite simple: you unscrew a big screw on the side of the watch and pull out a long aerial and the watch automatically transmits. So when I'm ditched somewhere in the Pacific Ocean, passing aircraft will be able to pick up a signal 200km away. And it also tells the time.

Fortunately, I've not had to use the watch, but it's definitely a nice security blanket to have. There are times, though, when you'd still be in trouble. When the sailor Tony Bullimore capsized in the South Pacific, there were few planes around to pick up the signal, even if he'd had the watch. It is a last resort, and the balloon also has othersafety mechanisms.

I was given the watch by Breitling a couple of years ago, after I had done the round-the-world hot-air balloon challenge. Unfortunately, though, we didn't get to do the entire trip because we were refused entry to China. When my fellow competitor Richard Branson's team strayed into forbidden Chinese airspace, they effectively prevented any other Britons from crossing China.

It was a nice sporting gesture by the company; these watches cost about £3,500. My partner, Andy Elson, wears his all the time. His is orange and mine's blue.

People often come up to me and ask about the watch because it looks really serious. It has a compass around it, plus a number of electronic programs and a stop watch - and the best party trick of all is when you are crossing time zones, you can simply spin the screw and it automatically goes round the hour without altering the seconds. I always show people that and they think it's fantastic.

This watch is probably the most personal gadget I could own, because it could save my life - that makes it a nice thing to have around your wrist.

A lot of equipment has trickled down to us from advances in the aviation industry. The greatest of these are global positioning satellites. You receive a signal from satellites and they tell you your speed, location and altitude, which is updated every two seconds. Although nothing replaces the compass, it's definitely much more reliable than sextants and the star-watching practiced by the ancient mariners.

Our capsule on the air balloon can only hold a certain amount of equipment. The capsule is big enough for the two of us, 12ft by 5ft, and we have a bunk each. There's also a flight deck, a very small toilet and a tiny galley with a kettle for cooking.

Obviously, communication is important. In the capsule we have a satellite telephone and fax machine. But you're a small space under a big balloon, and the telephone signal sometimes doesn't get through. The satellite fax, on the other hand, works almost faultlessly. We're constantly sending updated information to our mission control. No one is allowed to phone us, though, because we can't predict the workload and it could be a dangerous time.

There have been huge safety advances in the last 20 years. The first hot-air balloon flight was in 1783, and I've heard terrifying reports of damp sponges being used to put out fires in the middle of the sky. In 1981 the first hot-air balloon flew through the whole night. With navigation and safety advances we've been able to do much more since then.

Incidentally, I was the one who made that night-time flight.

Colin Prescot's book, 'To the Edge of Space: the adventures of a balloonist', is published by Boxtree on 5 May, price £20