Fame has put the world's first cloned sheep on a diet and left her co-creator, Ian Wilmut, feeling a little frazzled. Julia Hinde reports

Dolly's on a diet. The world's most photographed sheep has finally succumbed to media pressure. Too many photo sessions, enticed by offers of tasty sheep pellets, have left nine-month-old Dolly with middle-age spread. Now a sign above her pen says - "Hay Only".

Journalists and school children are still beating their way to the country retreat of the world's first clone at the Roslin Institute in the shadows of the rolling Pentland hills near Edinburgh, three months after she first made headlines.

And Dolly is not the only one feeling the pressure. Ian Wilmut has been astonished by the frenzy surrounding his team's creation. "I never thought it would be on this scale. There have been moments of real pressure. After all I had a full-time job before all this started," he says. "There have been times when I have been fairly seriously distressed over the past couple of months".

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When Dolly was announced it was decided that Dr Wilmut would front the show on behalf of the institute. Yet he was just one member of the team. He openly admits that he is largely not involved in everyday processes of genetic nuclear transfer, and at scientific meetings he starts by crediting his co-workers. But irritation is manifest, if initially denied. The constant presence of the media, three months on, does nothing to help. Continuing research is interrupted, while the constant presence of a camera crew, whether following Dr Wilmut to his allotment or down to the farm, is leaving a sour taste.

But Dolly has also meant wonderful opportunities for the Roslin team. Where Wilmut and his co-workers once received invitations to speak at conferences every few months, there is now a steady stream of requests. Wilmut has already filled his diary with British and international engagements up to 1999.

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"It's difficult to say no," he adds, laughing. "The extent to which you can inform people about the science and make them excited by the good things and not unnecessarily worried about the bad is very welcome. The more people know about this technology the better able they will be to make a sensible judgement of how it will be used. As long as I can cope - the difficulty is drawing the line."

Publicity will, he hopes, ensure more money for this area of research, providing security for a programme that has had to battle endlessly for support. Roslin began a programme of genetic modifications for farm animals in the mid-1980s, and drew on attempts at nuclear transfer in cattle by scientists in Calgary, Canada. The idea was that if they could combine such transfer with what were hoped to be precise modifications in embryo-derived stem cells, a large population of genetically modified, identical cattle could be created for breeding purposes. At that stage cloning of cells from adults was not on the agenda.

But obtaining British backing for essentially speculative research proved problematic. It took several years, says Wilmut, who, at that stage, with only one research student for support, considered taking his work abroad.

"It's very difficult to get blue sky money," says Wilmut. "Even now when it is a demonstrated good idea, it's not easy to get such money," he adds, referring to his own group's battle to secure continued support.

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"I think it will be relatively easy to get money from industry to, as it were, apply the technology. But what we also need to do is the basic science to make it better and to secure our position. It is proving more difficult to get that money. We have had a very low success rate with foetal, embryo and adult cells - we need to try to understand why and to suggest improvements in our methods."

Now confident that his group will eventually get the money needed to expand further, he adds: "Predicting the outcome of science is impossible. A lot of people said cloning was not possible. So if you can't predict science what that means is at least some of your effort has got to be roaming. I still believe that it is part of government's role to provide money for 'just looking' research."

Wilmut, who says he is now keen to investigate the nuclear transfer technique as a way of creating genetically identical, but precisely modified animals, adds he feels that so far the British and American governments have succeeded in fostering sensible debate and preventing panic legislation on cloning. This has not been the case everywhere. In Italy such research has been banned as a result of the British work.

As for the possible cloning of humans, Wilmut stands by his belief that any such attempts would be selfish and undesirable. "There are people who in response to really desperate situations, like losing a child in an accident, think they would like to make a copy of a person. People have got to understand that you would not produce the same person," says Wilmut. "You can't bring back someone who has died. There would be the fact that if you made a copy of that person they would be born at a different time. Even if they were born just ten years later, think how different things would be."

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He adds: "Above all, I don't think you could treat a new child in a normal way. You would know that the other person did certain things. There are so many expectations that we impose on our children anyway, just think of the extra ones which would be there on a clone. That is why I think it's selfish to think of cloning humans and I would be sad if it were done."