 Could you give me an example of where animals containing human material has produced some type of benefit? One good example is that it's possible to replace a mouse's liver with human liver cells such that almost all the liver of the mouse is now composed of human liver cells. And these mice are incredibly useful for studying a range of problems, but particularly for studying hepatitis C, for example. The only other animal model that you can use to study it is the chimpanzee because other animals do not get infected by hepatitis C. So by creating mice with human livers, you can now study hepatitis C in mice rather than using chimpanzees. And I think that's a very clear example of the sort of benefit you can get from this type of model. However, just to emphasise, we felt if you can replace a whole liver from a mouse with human cells, well, you might be able to do this with other organs. And that's where we got slightly concerned if you could do this with the brain, for example. So what if you put a lot of human cells in an animal's brain? Would that change its behaviour in some way? Unlikely to happen with a mouse or a rat, but if you had to do those experiments in larger animals, whether they were cats or dogs or non-human primates, then that's a big concern. There was a big fuss made a few years ago about a mouse which had what looked like a human ear on its back. There was absolutely nothing human about that ear in that particular experiment. It was, I think, cartilage made from cow, I think. And it was seeded with mouse cells. There was nothing human about it at all, except it looked a bit human. And people got very upset about that. It was suggested that some experiments should not be permitted, they were classed as category three, and they shouldn't be permitted at least for now. So if you were to take an early embryo from a monkey and introduce human embryonic stem cells into that, no one can predict what's going to happen, what the contribution could be. So we felt that that sort of unpredictable mixing of early embryo cells at the very early stage where you can't predict what's going to happen is something that at the moment should not be permitted. Were there any examples of where the public views and the expert views differed? The views from the public and the experts were surprisingly all in accord with each other. So the public were quite willing to accept the vast majority of experiments because they could see there was a potential medical benefit from this type of work. They only got nervous when you sort of crossing the boundaries between what's animal and what's human. And exactly the same reservations were clear in the professionals as well.