He remembered this experiment and it's called the Diels-Alder reaction, in which you take naphthalene – no, anthracene – and you interact it with a cyclised form of maleic acid. And what comes out of it is an extraordinary ring system called bicyclo-octanes, and this has got two ring system and two aromatics and you could functionalise the bridge between the two. And that was our lead, when we took these bicyclo-octanes very quickly we got into a... and in the standard way which we do the old fashioned chemistry: you make the compound, you test it, you learn from it, you make another one, and you iterate through it, and we iterated through it and we got better and better and better compounds. Now, one of the compounds we came to – a beauty, one of the best compounds I've ever worked with – it only had one problem and that was the liver couldn't distinguish it from a... a bile salt, and it was eliminated in the bile with the speed of light. And we could show that, in fact, it was absorbed extremely well, up the portal vein, but the liver was cleaning it out so that we'd get hardly any blood level, so the drug wouldn't act orally, but we could give it intravenously. Well, there wasn't much you could do with a drug you could only give intravenously. And then we read a paper by... that if you take nude mice – these are mice which have a suppressed immune system – so if you put a foreign protein in they don't react to them, so you can take cancer cell lines and embed them in these and... and they'll grow. Well, this particular cancer cell line was pancreatic cancer cells and so this group in Philadelphia showed that when these tumours were growing, if you gave them gastrin, they would go like mad. Anyway, so she tested our compound and showed that we could block that effect of gastrin and, indeed, we reduced the rate of growth of the tumour itself as though the mouse's own gastrin was stimulating the growth of it.