It started during the war, when I was working as an aircraft engineer. When I realised that it would actually pay, if you could do it, to design an unstable aeroplane. I should explain that aeroplanes have tailplanes and fins on the back for the same reason that darts have feathers on the back. If you throw a dart and it sort of goes off course a bit, the wind on the feathers bring it back straight, and if an aeroplane sort of slightly goes up or down, then the wind on its tailplane brings it straight again. If you took it off... if you took the tailplane and the fins off, then the aeroplane wouldn't be stable and the pilot couldn't fly it, because as soon as it started veering off, he wouldn't be quick enough to bring it back on. But for reasons, sort of... some of them are obvious and some of them aren't, if you could somehow design an automatic pilot to design the unstable... to fly the unstable aeroplane, it would be a good thing, at least in military aeroplanes, it would turn round corners quicker, it... it would find it easier, you see, to turn corners, and it would have other advantages. And I thought about this quite hard in, oh I suppose '44 or so, '43 or '44, but it was clear at that time that the electronics weren't up to it, we just couldn't make the electronic machinery to work. I'm told, by my young friends, that there are aeroplanes out there today, military aeroplanes, which rely on this principle, there are much better electronics nowadays.