For comedian and activist Mark Thomas, a Portlaoise school was a natural starting point for his book on the arms trade, writes Brian Boyd

You've probably always wondered what music would be played if you rang an arms dealer company looking to buy some electro-shock torture equipment and were put on hold. In the case of one company it's Love Me Tender by Elvis Presley. We know this because it's recounted in British comedian and activist Mark Thomas's new book, As Worn By the Famous Nelson Mandela.

In researching the book, Thomas talked to a very motley crew of arms dealers, torture equipment manufacturers, interrogators and politicians.

Moving through South Africa, Ireland, Saudi Arabia and Indonesia, he exposes a disturbing world of greed, political ineptitude, and persecution - the latter mostly at the expense of the most vulnerable people on the planet.

It all begins, curiously enough, with students from the Scoil Chríost Rí secondary school in Portlaoise. "The Irish angle was vital to the book," said Thomas on a visit to Dublin last week. "I found out that Ireland was one of the very few countries in the EU that doesn't have any brokerage laws - what this means is that you can set up an arms company here and begin trading weapons. This is what we did in the school in Portlaoise with the help of a great teacher called Sr Barbara Raftery. The students were able to purchase leg irons and they also brokered electro-shock batons to be sold on to a different country. The students were stunned as to what they were legally able to do. This was all done with the help of Afri (an Irish NGO) and the whole episode was broadcast in a Channel 4 show called The After School Arms Club earlier this year."

As a result of the programme, the Irish government promised to introduce anti-brokering laws. "They said that when the programme went out, but they haven't done anything about it," says Thomas. "The situation, as it stands, is ridiculous. I don't understand why they won't change the laws - it's hardly a vote-loser, is it?"

Mark Thomas is a very irritating person. Irritating, that is, to those involved in corporate wrongdoing and political corruption. Although nominally a comedian, he has long since left behind the traditional concerns of the comic and ventured instead into geopolitical territory, where what he finds is presented in a series of live shows that rely more on tragicomedy than anything else for their potency.

"It's political comedy but I see it more as highlighting something that is so obviously wrong," he says. "I do realise that I'm talking about torture, weapons of destruction, warlords, gangsters and child soldiers, but that is the nature of the material.

"This book was a huge investigation into the international arms trade and how it works and who it benefits. People ask me if I see myself as more of a campaigner than a comedian but for me it's quite simple: I go off and have adventures in the world of the arms trade and come back and tell the story."

The book's startling title comes from an actual phrase used by a torture equipment company to publicise their range of leg irons. Because they sold the same ones that were used on Nelson Mandela when he was incarcerated, they obviously thought it made for a nifty slogan.

"Mad stuff happens in this world," says Thomas. "One time I found myself talking to someone who was telling me all about this device called an 'interrogation foot heater' and how it went in temperature from 20-200 degrees Celsius. Another time, I found myself talking to the man who had sold the Kalashnikov machine gun that was used in the Hungerford massacre (when 16 people were killed in an English town in 1987)."

What Thomas didn't bargain for was getting to know so many arm dealers. "It sounds really strange, but one or two of them I sort of liked," he says. "What I mean is, I liked them as people but despised what they did. That was a strange ambiguity going on there."

He fervently hopes that the book will kick-start a discussion about the global arms trade and that at some stage there might be the prospect of an international arms trade treaty.

"You will hear the argument - from politicians usually - that doing away with the arms trade is bad for business and it would lead to job losses. But these were the exact same reasons put forward for not abolishing slavery," he says.

The book, for Thomas, is the culmination of 10 years' work as a campaigner.

He originally emerged from the "alternative comedy" circuit but always distinguished himself from his peers by dint of how thoroughly he researched his subject matter. His Channel 4 series, The Mark Thomas Comedy Product, saw him tackling an array of politically sensitive matters - in one show he ambushed a train carrying nuclear waste by taking over a level crossing with a couple of armoured cars.

Such was his prowess at exposing political corruption that an ex-Labour minister, Richard Caborn, once sent an e-mail to civil servants asking them to gather "background dirt" in order "to rubbish him". The e-mail was leaked to the press.

"You can only regard something like that as a success," he says. "If a New Labour minister is trying to smear me, it's obvious that I'm doing something right."

Along the way he has been awarded a UN Global Human Rights Defender Award and also a Kurdish National Congress Medal of Honour - the latter a result of his work on a three-year campaign to stop the building of the Ilisu Dam in Turkey. The campaign was successful and helped save an estimated 78,000 Kurds from being displaced.

"The point about all this is that change can happen," he says. "People sometimes feel helpless when faced with all these gross iniquities but once you get involved in these campaigns you become much more aware of your power as a citizen and how you can engage in the political process. Individuals I know have sued governments - and won. It is possible."

Not so long ago, Thomas found himself being called to give evidence to a select committee in the British parliament on the arms trade. "That was a strange moment because I realised that I had gone from tying myself to buses that were carrying arms dealers to speaking to a select committee about the arms trade. I still don't know which one of those actions was more worthwhile . . ."

•As Used on the Famous Nelson Mandela: Underground Adventures in the Arms and Torture Trade is published by Ebury Press, £10.99 (paperback)