We were given the prime task of finding a solution with great urgency to this night fighter problem of how to devise an air interception radar system, working on a much shorter wavelength to avoid the ground returns. I then worked on the problem of the aerial system and I first of all substituted small paraboloids instead of... instead of these great horns and we gradually assembled the equipment. I had a split anode magnetron, working on 10 cm. A very, very low power and measured a polar diagram and also how one could displace the narrow beam from... by moving the focus and so on, by moving the dipole of the focus, and we gradually assembled complete equipment.

And then, I think, it was in June or July, Oliphant from Birmingham arrived with the new device, a Cavity Magnetron. Now the story of the cavity magnetron is that in Birmingham, Oliphant had a contract from the committee development to work on this problem of producing a device which would generate sufficient power at very high frequencies. And it was in February of 1940 that Randall and Boot had working on the bench the first of these cavity magnetrons, which astonished and it is now extremely well-known how they were gradually led to the use of a series of cavities, of resonant cavities, through which the electrons moving in a magnetic field would generate these very high frequencies. And, of course, they had this working on the bench, and it was very, very far from any device which could be used in an aircraft, but GE's, General Electric company, and particularly Megaw. They transformed this cavity magnetron working on the bench to a sealed off version, and it was this beautiful sealed off version, the first one which Oliphant brought to us at Worth Matravers in June or July. I think it must have been June of 1940, and so we built this into a... a potential air interception equipment. Now, we had the thing working and there was a lot of discussion with the General Electric company who had also been given a contract to work on the problem of devising an air interceptions system, working on a much higher frequency and they had managed to... they had devised what was called the micropup, in which the outer casing of the... of the valve was the anode and this so reduced the electron transit time that it would work on a wavelength of about 25 cm.

So we had a system on 10 cm, and they had a system on 25 cm, and one day in August most of the senior members of the group had gone to liaise with General Electric company about the use of an aerial system and so on, and I was left at Worth Matravers, I think it was August 10th or 11th, with Bill Burcham. Now, Burcham was another of Rutherford's young men who had joined us during that summer and he and I had worked together, assembling this equipment. And I had two paraboloids, one for receiving and one for transmitting, working on a movable framework. And others had built a modulator and a transmitter and Burcham and I happened to be there on this afternoon alone when we had this equipment working.

And suddenly an aircraft had begun flying along the coast and lo and behold, there was an echo on the cathode ray tube, and I believe that this was the first radar echo from an aircraft ever seen on the 10 cm equipment. Well, of course, the effect of that was like an explosion. I mean, immediately all the big wigs assembled to see a repeat of this, that 10 cm really would be useful in the detection of aircraft. That was in August 1940, and there... there we were, in the midst of the Great Battle of Britain, with the chain stations doing its job. The trouble was, of course, that we were short of Spitfires and Hurricanes and shorter still of pilots, and therefore the great value of the stations was that they could direct the pilot to an invisible range during day of the enemy and that saved us, but nevertheless our work was greatly disturbed. We were constantly being machine-gunned and ordered into air raid shelters. And we could see some of the great battles in the Battle of Britain taking place to our left over the Isle of Wight and to our right, over Portland, and it was really unforgettable and dramatic. But the... the disturbance to our work became too great, and we were moved to... lower down to... we took over a place called Langton Matravers. It was a girls' school, Leeson House in Langton Matravers, and the other parts moved to other places in Swanage and Langton Matravers. The workshops did remain for some time at Worth Matravers and I think they were then machine-gunned and I think there were fatalities. Furthermore, by that time Worth Matravers had become an operational chain home station.