I do believe what you’re thinking of was post World War II when the Labor government gave British jet engine technology to the Russians and those engines were later copied and using the Mig 15 fighters
Tophat, IMMIC they did in the 30's with the Merlin! He was in the House of Commons and spoke out about it, it was one of their efforts to reach out to the German people. Stuuuupid.... Sadly I can't find a link to it.....