At the same time that we first used the equipment operationally over Germany, we learnt that the cabinet were severely worried, the war cabinet were severely worried about losses to our U-boats and merchant shipping in the north Atlantic. And it is perfectly clear from Churchill's memoirs that his one anxiety that Hitler at that time was to stake all on the U-boat campaign. Now, the point there is very interesting as far as our equipment is concerned. Coastal Command did have what is called ASV, anti... submarine... anti surface vessel radar and it was only about 1.5 metres. The Germans had captured the west coast ports of France, which they had used as a base for their submarines crossing at night to get into the shipping lanes to the North Atlantic. And they would surface to charge their batteries, because they had no snorkels in those days, but they could be attacked by the Coastal Command planes, using this 1.5 metre ASV, and they would be depth charged and severely hindered.

Then they discovered a very simple means of evading that. They built themselves a small receiving set, called Metox which they put in every U-boat and that easily picked up the radiation of the 1.5 metre from the Coastal Command aircraft and as soon as the signal was obtained, U-boats would dive and so the attacks on the U-boats went to almost nothing, and the shipping losses... when we first became aware of this in late 1942 and early 1943, this had risen to terrible proportions. We were then losing half a million tons of merchant shipping a month and this was expected to rise to something like a million tons a month by the end of January and February of 1943. Now, I think that if that really had happened the outcome of the war would have been entirely different. We would have become short of food, and the German... the American army certainly could not have been safely brought across the Atlantic. Anyhow it seemed to us that there was one simple answer to this, to change the wavelength and to use some of our H2S equipment on 10 cm and put it in the Coastal Command aircraft. Do you know the Coastal Command were moderately interested. Bomber Command were violently opposed. Harris said it would be much better for them to use the equipment to bomb the U-boat pens, which was a lot of nonsense of course. So in the end we – my own group in the lab – we more or less converted half a dozen equipment and got permission from Renwick to fit this in six Coastal Command aircrafts operating from Chivener Airport.

Now, in February of 1943... in fact, almost as soon as I had returned from the first operation, the Bomber Command over Hamburg, I drove to Chivener in North Devon, where I now had half of my staff trying to maintain this equipment. They wouldn't let me fly out of the country, but I managed to... someone, I had nothing to do with this but someone managed to persuade the authority to allow a rather senior member of my staff, Fortescue, to go into uniform and become the operator of one of these first operations over the Bay of Biscay. So I think it was then the first week of March that I was at this Chivener Airport and Fortescue took off with our hooked up centimetre ASV, for the patrol over the Bay of Biscay at night, and the station commander... fortunately I've forgotten his name. He was very irritable and I remember the dawn of the day they were meant to return, and they said, 'Look here, young man, your foolish equipment. What the hell good do you think that's going to do over the vast ocean expanses?' And he said, 'You should go out and see for yourself'. Well, of course, I would have loved to have gone out and seen for myself, but I was not allowed to.

Anyhow, the situation changed because the squadron returned. They'd had no contact with U-boats, but Fortescue had detected that they were being chased by a German, I think, a Fokker Wolf and he gave the instructions evading action, instructions to the pilot to take evading action, and of course that completely saved them. When he reported this on landing, that put a different emphasis altogether on the situation, and I think the next night the report said a U-boat was detected, showing no signs of expecting attack and was depth charged. Well, in March and April, that squadron from Chivener, using the centimetre equipment, only half a dozen of them by the way made 24 depth charge attacks on the U-boats crossing the bay and, fortunately, at that time the people at Bletchley had broken the naval code and the situation, the U-boat... Dernitz ordered the U-boat to stay on the surface and fight it out. They were harrassed and depth charged by our equipment across the bay. I think 24 were lost in those two months in trying to get across the bay and the... by the end of May... you can read this in the official report on the Naval warfare, written by Roscoe, who said he could still feel the heat of the sigh of relief in the Admiralty when Dernitz ordered the remaining U-boats to return to their home ports. And the shipping losses in the North Atlantic, they suddenly dropped, and in... I think it was in August of that year they'd fallen to instead of being one million tons a month, they'd fallen to less than 50,000 and Hitler in a radio broadcast said that the temporary setback to our U-boat campaign is due to one single technical invention of our enemies, and this was the Cavity Magnetron, used in our equipment.