Can we take that story up, Laura Piddick? So he's found this, but we still haven't quite got what he was looking for with these pet traditions.

So he really goes back to just before the First World War, where he was already a microbiologist at St Mary's Hospital. And he recognized as a good scientist, but he was also part of the army. So he was in the World War One as a field hospital, and he was shocked by the number of patients who died because of the blast wounds. And this is the first time they've been blast wounds. We recognize them in modern warfare, which blasted in bacteria, which then got into the body called sepsis and died. So in the bloodstream, and they had very early times where they could put antiseptics into the wound. And he found that whilst the antiseptics were very good on the surface, it actually did a lot of damage when it got into the wound. It actually stopped some of the body's healing processes from working. So at the end of the war, he went back to St Mary's into his lab and started a long period of work looking for antibacterial substances made first of all in bodily secretions, which led to lysosine, which you just mentioned, but also led him to look in all sorts of other ways for antibiotic type substances.

We're talking about bacteria. We are 90% bacteria. How do you distinguish them that's trying to get us and them that aren't?

That's a very good question. And we still struggle with it today because we well recognize friendly bacteria and bad bacteria. The reality is bacteria can be both and we need bacteria inside us for our gut to work properly, to be able to digest our food properly. We need it for defense as well. They often perform a barrier and on our skin. So the real, when they're bad, is when they get somewhere they shouldn't be, such as in the bloodstream, for instance. So body site, we would not expect a bacterium to grow in.