Here's the point I mentioned earlier, the accident: that we got to beta blockers from adrenaline taking the natural compound and manipulating it. And I did that because I couldn't think of anything else to do. Now, we go to Smith Kline and we're in the same position. I want to block the effects of histamine and I know the structure of antihistamines, but they don't do the job I want. So where to start? So, that's when – more self-consciously – we started making analogues of histamine, and... and that's where you were involved and so on. Anyway, they... the analogy here is that one of the earliest compounds we made was the guanidine analogue of histamine of the terminal. And it was tested and found to be just like histamine, and so it was ignored. And we went on, I think, four years, Bill, and tested and tested and tested them, and just got nowhere. And now this is the kind of place where... is it recollection or reconstruction? I fear it's reconstruction but my reconstruction is that I remember... so this is my... my reconstruction, sitting with Mike Parsons, who was the pharmacologist who was doing the work, and going through all these structures. And, again, we had now changed the method of assay and I remember fingering this compound and saying, 'Why don't...?' And we found that it was to histamine like DCI was to adrenaline; that is, in certain circumstances it would be a powerful stimulant. But, anyway, that... we then... we got to beta blockers from adrenaline by attacking the hydroxyl groups on the ring, replacing them the analine. Histamine is imidazolethylamine, and so I was expecting that we would have to do something to the imidazole ring. And a lot of our chemistry, you know, very difficult chemistry because of the solubility of these things... they didn't come out of solution easily, was making benzimidazole and all kinds of things. You remember. And so now this was... changed not on the ring but on the side chain. And so, anyway, once Ganellin and his chaps got the idea there was no holding him back then, and we went from that eventually to cimetidine, and into man.