Ian Wilmut does not look or act like a man who has changed the world. In his unremarkable office at the Roslin Institute in Edinburgh he is unprepossessing and a bit shy. He strains to make small talk and his hands tremble a little. He is dressed as if he last shopped for clothes during a 10-minute wander through Marks & Spencer in 1975.

The screen saver on his computer displays a photograph of his three-month-old grandchild. Around the baby are admiring adults, their eyes gleaming with wonder at this everyday miracle of new life. The proud grandfather, in particular, is something of an expert on miracle births, having had a hand in a very special one on July 5, 1996.

On that day, a Finn-Dorset lamb was born at Roslin’s animal research institute south of Edinburgh. It was the world’s first cloned mammal, an exact genetic copy of her mother, grown from an adult ewe’s mammary gland.

The mammary was the inspiration for the name given to the newborn lamb — Dolly, after Dolly Parton. It was a poor joke, but an indelible moment in scientific history.

“I didn’t quite appreciate what it would mean for me,” admits Wilmut, “and you’ll think I’m very naive for saying that. We had gone through the tidal wave of publicity in the first four weeks and my wife and I went down to visit family in North Yorkshire. I remember saying to her that in a few months it will all have gone. And, of course, it will never go away.”

When Wilmut is talking about cloning, his voice steadies. The tone is measured and the demeanour slightly more relaxed, his natural reticence quelled. On his chosen subject he believes it is important for the world to listen, because he is foretelling the future.

The birth of Dolly opened up the possibility of human cloning and changed the way we would think about individuality and identity. For future generations, some certainties would no longer hold. All your personal strengths and weaknesses, in body and character, might already have been tested in life by someone else with exactly the same DNA. It would become more difficult to claim with certainty that you were truly your own man. Somebody else may have got there first.

For the past seven years Wilmut has travelled the world talking about his research and is held in high regard by the scientific community. But now there is a new purpose to his work. Earlier this month he and a group of other world-renowned scientists visited the United Nations in New York to talk to a gathering of ambassadors. With the help of a video message from Christopher Reeve, the actor paralysed in a riding accident in 1995, the scientists argued their case against a proposed UN ban on human cloning. The UN will make a decision later this year, but already there are strong signs that the opponents of cloning will win the day. Powerful backing for the ban has come from the United States, driven by a president with theological objections to tampering with what he sees as God’s work, and the destruction of embryos that have within them the possibility of human life.

Britain is on the other side of the argument, believing there is a distinction between the two possible reasons for cloning a human being. In the UK, cloning with the intention of creating a baby — reproductive cloning — is banned. But cloning for research into degenerative conditions such as Alzheimer’s disease and multiple sclerosis — therapeutic cloning — is not illegal.

The use of stem cells from cloned embryos is believed to offer a realistic chance of curing such conditions in the next 10 to 20 years.

Last week the Human Fertilisation and Embryology Authority, the UK regulatory body, was preparing to announce its decision on a request by scientists from Newcastle University to clone a human embryo for medical research, using the same technique that produced Dolly. It would be the first licence of its kind in Britain. Wilmut is already working on producing stem cells from donated embryos and is preparing an application to conduct cloning for research into motor neurone disease.

Like the British government, Wilmut is against reproductive cloning but in favour of therapeutic cloning. A sweeping UN ban, he says, would dash the hopes of millions for a cure to some of the most distressing medical conditions known to science. “The problem is that it would create an atmosphere and set a tone,” he says. “It would make it more likely that the European Union would do something similar.

“The whole attitude to research with human embryos would step back a bit, and that would be to miss opportunities to study these diseases and perhaps ultimately to treat them.” A UN ban would not be binding, however, and Wilmut hopes Tony Blair would hold fast and refuse to sign up.

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