Psst! Do you want to be a spy? Well, possibly not quite so much as you did, given the gruesome fate of the former KGB officer Alexander Litvinenko. But thankfully science has contributed much more to the spying profession than radioactive poisons.

If you are anywhere between 5 and 12 years old, or just young at heart, you can see just what science has to offer spies, at the Science of Spying exhibition at the Science Museum. This is no ordinary display of sinister devices, or spy memorabilia from historic times — no sign here of Mata Hari’s kimono or Klaus Fuchs’s spectacle case. This is a living invitation to become a spy, in fun and just for a little while, and to understand some of the principles and mechanics of the trade. For the technically minded, there are some startling, very modern devices on show and for the serious-minded there is plenty to think about.

If you are going to be a spy, of course you have to have the necessary aptitudes, and learn your trade.One of my early training courses — called “Locks 1” — culminated in an exercise involving my attempting to pick the lock of a suburban villa in the pouring rain, which took me so long that my team colleagues, waiting in the shadows to make a surreptitious entry, risked alerting the neighbours with their chattering teeth.

When eventually we got inside, because this was an exercise, a police car soon turned up and we were all “arrested”. I never graduated to “Locks 2”. At the Science Museum,you get to burgle a combination locked safe — no good trying to pick today’s locks — by listening very carefully to the changing sounds as the tumblers fall. A difficult job, but at least there’s no danger of any blue-uniformed intrusion.

First, though, you have to show that you have the nerve required to be a good spy. Would you put your hand through a hole in a box without knowing what's inside? Would your hand shake as you tried to pick a stick of dynamite out of a cluster without disturbing the rest? If it does you’ll know about it!

Of course, I haven’t begun at the beginning, spies never do. They are always in the thick of things. The firsttest is to get into the exhibition, working out how your entry pass opens the back of the telephone box. When you are through, you are automatically enrolled as a spy and launched on your mission. This is not the world of James Bond or Q.

Today’s spies and counter spies need to show they have the necessary brainpower and analytical skills before they get to use the gizmos. So can you detect if someone is lying? Can you crack the Caesar cipher, all set up on a computer for you to try? If that’s a bit beyond you, can you choose the right disguise to merge undetected into the ambassador’s cocktail party (not the pink tutu, to be sure: you’ll soon find out that’s thewrong choice when you look in the mirror); what can you find out about a person by examining the contents of his rubbish bin? Yes, there’s a real rubbish bin, complete with smell.

Before you move on you’ll need to pick the right tools for an espionage operation, because you will be going on one. Of course, it does get a bit harder the older you are, but then that’s life.

Having tested your human skills, you have to learn how to collect the intelligence and how to communicate it. The technology centre is where you meet the gizmos and learn what amazing things they can do. When I was a child in the Second World War, the military used Morsecode to communicate and as a little Brownie I learnt how to send messages by semaphore. In the Cold War, agents passed information by dead letter boxes and brush contacts, always risky and liable to detection.

The exhibition offers a startling choice of tiny encrypted digital communications devices, disguised and concealed in cunning ways — didn’t I see that dead drop rock on TV, in use in Moscow? I’m delighted to say that in this feast of technology, Morse code is not forgotten; if small people get tired while their older siblings send enciphered messages, they can rest on a brightly illuminated computer key, which will amaze them by transmitting theMorse code for its letter when they sit down.

Judging by the exhibition, it is in the field of covert surveillance that science has made its major contribution. You can meet the Raven, a hand-launched remote-controlled plane no bigger than a kite, which can fly some 15 miles and beam back information and pictures of what itsees. Have you heard of the throw-able crawling camera — you can chuck it into the ground floor of a building and tell it to crawl upstairs — or the parabolic camera, which can turn its head to give you a 360-degree view?

Before you leave the Technology Centre you must create your false identity, by using the biometric face scanner to change your vital statistics and, if you think it will help, alteryour fingerprints with melted gummy bears. Of course, technology has always played an important part in espionage and counter espionage. It’s a race between the spies and the spied on, in which everyone conceals the best part of their hand. For everything you see at the exhibition, you can be sure there is something even more amazing up someone’s sleevethat they are not telling you about. The Science Museum has solved this problem by consulting technologists and scientists about the shape of possible future spy devices, and these are displayed at the end of the exhibition, in the FutureLab. Don’t be surprised if, as you walk through this part, you find yourself rubbing shoulders with sinister-looking characters in dark spectacles and macs with their collars turned up, trying to pickup a few hints. However, they won’t be writing in notebooks, they will be absorbing the information in tiny digital infohoovers.

Before you can get to the FutureLab, though, you have to go on your mission, using all the skills and clues that you have picked up. You have to find your way into a shadowy organisation, OSTECK, by choosing whether to go through the brain scanner or the body scanner. You will find that one will let you in, to become a spy on the inside, and one will let you spy from the outside, on what’s happening inside, thus solving your difficult problem of whether to join MI6 or MI5. Good luck, and don’t get caught or something nasty may happen.

The Science of Spying exhibition is very well conceived and researched. While offering a fun and exciting experience, it quite rightly avoids the James Bond approach. More than that, though, it will give the reflective 12-year-old some important issues tothink about. When is surveillance justified? Who should be using all the gadgetry that science has provided, and against whom? And with what checks and balances?

It makes the point that surveillance — or spying — has progressed well beyond its original border of war and international politics and has become a fact of life so pervasive as to challenge our freedoms and our privacy. Spying won’t go away, and it and its techniques are something we all need to know and think about. The museum will be holding family workshops in the holidays and sponsoring debates on the broader issues. They are certainly needed. The Science of Spying, Science Museum, London SW7 (www.science museum.org.uk 0870 9063890), Feb 10-Sept 2; prices: during school holidays, adult £10, child £8; during term-time, adult £8, child £6; group discounts and family tickets are available. Stella Rimington is a former Director-General of MI5

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