We also found very quickly that they were susceptible to mutagenesis, by a compound called EMS - ethylmethane sulphonate - and indeed, you can mutate their genes at about the same frequency as you can mutate the genes of the E. coli [Escherichia coli] that accompany them. That they are transparent to this mutagen. And that enabled us to get the whole of the genetics under way, and the first mutant was isolated in 1967. It was called E1. It's a very famous mutant. The E stands for EMS, because we thought we would name the mutants with this. Later the E stood for mutants isolated in Cambridge. What I decided to do at the time was to keep all the work that I would do open - that is all the lab notebooks - so that everybody could use them. And so each organism, each mutant was given a file, and into that file went everything that had been done with that mutant. That is, they weren't kept chronologically in my... in my own lab books, so that if we isolated, we put in the file how it got segregated, put in the file where you could find it, all the crosses had been... were put in the file with that mutant. And so up to about... this system was retained, all the... the books are there, there are a few hundred of them - they are stored and looked after in the Laboratory of Molecular Biology. But they contain all the raw data of every mutant and the things that I worked... naturally once the work began to expand and other people that... that stopped. So that's a history there embodied in those books of the contribution to that work.