if you search for the name H. J. Ovens on the London Gazette there is one long carreer officer shows up
Flt. Sgts.
9th Dec. 1943.
571035 Harold John OVENS (53687).
This listing indicates this airmans promotion too officer in late 1943, from being a Flight Sergeant he became commishionied as a Acting Pilot Officer.
http://www.london-gazette.co.uk/search and search for the 53687 number.
His NCO serial number above, indicates probably a former apprentice airman who enlisted somethime/anytime after 1926.
http://www.rafcommands.com/forum/sho...ervice-Numbers
Your friend might not be this man at all but since his promotions are listed all the way up to 1972 at least, I assume it is.