Scanned from a 1948 print from the original 1946 photo
An Avro 691 Lancastrian (passenger version of the Lancaster) being used as a testbed for jet engines
The aircraft shown had it's two outboard Merlin engines replaced with Rolls Royce Nene jet engines, in the photo the Merlin engines had been shut down with the Lancastrian being powered by the Nenes
Photo by English photographer Charles E Brown (1896 - 1982)