The Rolls-Royce RB.41 Nene was a 1940s British centrifugal compressor turbojet engine. The Nene was essentially an enlarged version of the Rolls-Royce Derwent with the minimal changes needed to deliver 5,000 lbf, making it the most powerful engine of its era. The Nene was Rolls-Royce's third jet engine to enter production, designed and built in an astonishingly short five-month period in 1944, first running on 27 October 1944. It was named after the River Nene in keeping with the company's tradition of naming its jet engines after rivers.