That was apparently awarded to this man, see his list of awards.
https://en.wikipedia.org/wiki/John_C..._(RAF_officer)
Also see footnote 98 on this page:
https://en.wikipedia.org/wiki/List_o..._(A%E2%80%93C)
Here is another man who got it, so I suspect there may be several such men:
http://www.bbm.org.uk/airmen/Greencp.htm
Update (based on the the links given by Col Bruggy below in the next post, the four RAF awards were to:
John Cunningham
Charles Patrick Green
Walter George Gardiner
Frank Anthony Robinson