Although it's not for me to decide, but if ASW22 is still with his head into the cumulus, Dave Wilson is spot on, would be my verdict. Made it too easy it seems.
Apologies to ASW22 for the complete hijack of your post. But please give us some more info (and any other nice historic pic's available??) of Irles-Grevillers.
Courtesy of 'Anciens Aérodromes'
Aerodrome-Grevillers-n043_20-03-2010_14-17-03 | Flickr - Photo Sharing!
Aerodrome-Grevillers-n072_20-03-2010_15-28-38 | Flickr - Photo Sharing!