re: #251 Targetpractice
There was one other fighter built with that airframe, the Tornado that used the Rolls-Royce Vulture engine. They had to cancel it for the same reason that the Avro Manchester ended up being re-engined as the Lancaster with four Merlins, namely the Vulture had a worrying habit of bursting into flames.
Everyone in that time period had issues with getting the bugs out of new and bigger engines.