This brings me round to the particular group that I was sent to when I joined TRE staff, concerned with airborne radar sets, AI, Airborne Interception. And when I got to this group they were just – the Air Force was just changing over from AI Mark 7 to AI Mark 8. AI Mark 8 was a rather strange device. It had a nodding antenna, but at the same time it was spinning round at a much higher speed, so that it, the beam from the, from this radar antenna described a cone, circled round in a cone. They had a Perspex nose which fitted onto the Beaufighter , and also onto another aircraft, which just accommodated this monstrous thing whizzing round at a very high speed. I don’t think the pilot had a display, he may have done, but he certainly had a navigator to operate the radar for him. And the display would be an arc of a circle, at a particular range from the centre of the circle, and the angular width of the arc would be a measure of how far it was away from the centre line of the aircraft. And as the pilot directed the aircraft at the target, this circular arc became longer and longer and eventually became a complete circle. So that the pilot could fly the fighter aircraft constantly with the echo adjusted to be a complete circle and not broken at all. He could see that he was overtaking the target by the fact that the circle became smaller. And eventually he could see the thing and shoot it down.