Torres,
Yep, the Oxford was designed by Airspeed, of which Nevil Shute Norway was a founder. I think a guy called Tiltman designed the aircraft (basically a military version of their Envoy "airliner" I think) and Norway's involvement would probably have been stressing the aircraft. He was also involved in the design of the R-100 (the one that didn't crash!).
Read his autobirography "Slide Rule" recently - interesting stuff.
Cheers
Treadders