Hodgkin remained in charge of the air interception equipment, and I was transferred to another problem with night interception, but I ought to say, before I deal with that, about the general situation of the night defence, Tizard, who believed that when the Germans had been defeated in the night battles, in the day battles as they were, they would quickly turn to night bombing. And they did so, and in the autumn and winter of 1940 there were these terrible raids, our devastating raids on London, Coventry and the other cities, and really the ack-ack guns and the night fighters could do little about it. They had very little success but it was not our 10 cm equipment that transformed the situation. It was the fact that the improvements in the original 1.5-metre system... a firm had been drawn into this, EMI, Electrical Musical Industries, and they had probably the most brilliant electronics engineer in the world working for them, Blumlein, whose name will appear as a tragedy later on. And it was Blumlein and his staff who really put good science into this 1.5-metre equipment. They rebuilt the transmitter, they rebuilt the receiver and they used the modulator so that the tail of the pulse, which went out originally from the transmitter, which was I should have said a swaging device, had a long tail and so we now had sharp pulses.

Furthermore a system of controlling the night fighter from the ground, known as GCI, Ground Control Interception had been developed and the prototype of this system had been built on the cliffs of Worth Matravers just below where we were working. And on this one could see the... both the approaching bomber and the night fighter, and one could guide the night fighter into, into range above that... below that obscured by the ground returns on the 1.5 metres, and it was the night fighter, the improved 1.5-metre air interception equipment under ground control, which dealt with the night bombers.

The first operational contact occurred, I think, in November of 1940 and by that time the equipment was being put in a new night fighter called the Beaufighter. The Blenheims were fairly useless. They were too slow and then their armour, their machine guns were not capable of dealing with the German night bombers, but the Beaufighters were equipped with a cannon and it was in the early months of 1941 that the historic people like Cunningham devastated the German night bombers. And by the spring of 1941, more than 10% losses were being inflicted on the German night raiders, and that was beyond... they could not sustain that. That was really the effective end to the night raids... there had been sporadic bombing afterwards and elsewhere. But it's very interesting that the point I'm making now is what really dealt with the night bombers was the original, continued improvements and the application of experts and skills and techniques into an original system under ground control that defeated the night bombing system, the night bombing raids. The 1.5, the 10.0 cm system which Hodgkin and others tested in a Blenheim in the spring of 1941 again went on with enormous speed and by one year later, in March 1942, this 10.0 cm AI interception equipment with Hodgkin's spiral scanner was in operation. In March 1942, that is a year after the first flights in the Blenheim with the elementary equipment. You know somebody was once... going ahead a bit after the war, I gave a lecture to the Aeronautical Research Council and someone asked me afterwards why things could be done so quickly during the war. And I said, 'Because nobody ever asked us the cost'. The question was, 'Can you do it and when can we have it?' And that had a big impact on my future story of the war.