Personal Column: The spy who loved it

MI6 doesn't like gadgets such as hollow rocks. Former agent Harry Ferguson reveals some trade secrets

I was involved in all the things that you would expect a member of MI6 to be involved in - the recruitment of agents, the running of agents and covert direct action. There is no average day. Spies of all foreign intelligence services spend time abroad, and when you are in the field you don't know what the next day is going to throw at you.

Real spies hate gadgets. The rock in Moscow is a perfect example why. If you get caught with one there's no talking your way out of it. So wherever possible we'll just use a normal camera. If you're going under tourist cover it's perfect.

If we can't use normal kit we will try and get something you can buy off the shelf. So if you're caught with a concealed mic you can say that you're a private detective or you suspect your wife is having an affair. Nine out of 10 gadgets used are involved in agent communication. Most of the rest are for copying information or for recording in a concealed way.

What you won't get is things that are used for killing people or defence. By the time guns are produced it's too late, so we don't go around with knives in briefcases and guns in shoes. You do have a lot of ex-SAS and ex-SBS boys turn up at training courses, but they show you how to kill someone with your pencil. Spies are taught to use things around them. A ballpoint pen isn't suspicious, but used the right way you're just as dead as if I'd shot you. You don't have to kill with your bare hands, because there is always something you can use.

Surveillance has changed. The "three-man follow" is still used, but these days they are backed up with all kinds of digital gadgets. There are sticky cameras now, no bigger than a thumbnail and that you can bang on a pillar box or wall, which will relay a really good picture back to a base station. So you no longer need people in line of sight. They can fit cameras to car aerials, the technology is so good.

Dead letter boxes - a place where you could leave a message - have been replaced as electronics have improved. You could have a small box with a keypad like a mobile phone and the agent would key in his intelligence - "the bomb will be planted at 9pm next Thursday", say - and he presses a button and you pick it up in your box across the square. This idea of having a remote station, which is what that rock was, is an extension of that technology.

The best cover is not necessarily the person who sits in the background, whom nobody notices. In the 1960s one of the most successful agent runners was known as a drunk and a philanderer. Introduced to Khrushchev, then leader of the Soviet Union, he said, "I'm the MI6 man here", and no one took him seriously. If you are abroad and are looking to recruit agents you want to meet a lot of people and have to hold a lot of parties. You can't do that by being the grey man.

I was recruited through what was then the classic route. I got the tap on the shoulder while reading modern history at Oxford. One afternoon a tutor said: "Would you be interested in working for your country abroad somewhere?" Today you can log on to the MI6 website and apply.

In the old days there used to be a lot of diplomatic cover. Now, as the targets have changed, the Cold War has disappeared and the "war on terror" has begun, the range of covers has become much broader. These days they quite like to take people in their early thirties when they have established themselves in another career. So if you've worked as a radiologist, for example, we could give you all kinds of medical covers. There are certain covers we won't use. By and large we would avoid charity workers or ministers of religion because of the repercussions if they are found - the particular charity or church could be directly targeted. The key word in espionage is "deniability", but all the time you have to ask, if it doesn't work out who will get hurt?

Spying isn't as dangerous as people think. There are moments of danger. but the thing about being a spy is that you're very well prepared. The best thing is the secrecy. You're at a party pretending to be Joe Bloggs visiting a country with such and such pharmaceutical company, but all the time you know who the goodies and the baddies are. The access to this secret world is a tremendous thrill.

The worst thing is not being able to tell people that you know all this stuff. I was involved in some fantastic things, but it's absolutely forbidden to talk about the people I knew and what happened to them. You could have saved the world, but you would never be able to tell anybody.

Harry Ferguson's books include 'SPY' and 'Kilo 17'. His latest, 'Lima3', is published by Bloomsbury at £10.99. He was talking to Julia Stuart