Once the Rad Lab got involved, the UK focused on more theoretical or foundational aspects of the technology and let the Rad Lab develop the actual weapons syste

Once the Rad Lab got involved, the UK focused on more theoretical or foundational aspects of the technology and let the Rad Lab develop the actual weapons systems. The anti-submarine radar was a good example: the British developed the sea-scan radar, but testing showed it was very difficult for a bomber crew to use it to actually get the plane on-target so the Rad Lab developed the radar-driven autopilot and integrated it with the B-24s. I think the H2S radar was developed entirely by the British with limited US/Rad Lab involvement though. Amazing story about your grandfather! Actually the cavity magnetron played a key role in starting the Rad Lab. The US was still neutral at this point and Churchill decided to "gift" one of the prototypes as well as some scientists to explain how it works to the US in hopes that the US would create radar sets. On the way over the scientists decided to give the crew of the convoy ship a physics lecture, but they couldn't talk about what they worked on so they decided to talk about something that could not possibly be relevant to the war: nuclear fission.