I was quite surprised when I came across this video.
From my watching of movies/videos of WW2, I thought it was the Germans who first developed the jet engine for air planes, during WW2.
It appears the Germans may have used the information in a British Patent, by Frank Whittle, before WW2 started.
This is a gem of a video about all the difficulties Frank Whittle came up against, from the British government and Air Force, in his attempt to develop the jet engine.
So the British not only gave the Americans, during WW2, the engineering specs to their development of the cavity magnetron for use in Radar, but they also gave the Americans the specs for their development of the jet engine.
https://www.youtube.com/watch?v=G0T4-XG612Q