A few years ago while operating a radar mapping survey aircraft in a European country ( not France ) my survey area encroached on the ILS approach path to a fairly quiet ... non radar, medium sized airport...Radar mapping work can be carried on in ( non-turbulant ) IMC conditions and ATC were well informed as to our work area and were constantly requesting updates on our position. Periodically ATC used their own language .... we presumed for communications that did not affect us....
crossing the ILS approach at 90 deg. we suddenly exited from cloud into the clear to find a Fokker 100 very close on a definate colision course in our 10 o'clock...ATC had forgotton our last position and track report and cleared him for the approach in the local language. He broke into a very steep climbing turn left and I broke sharp right...the miss was very close..the turn he made bordered on aerobatics and I can imagine his pasengers being in a state of shock.... The pilot certainly sounded shaken when he finally calmed down enough to talk again....
It was to avoid this kind of incident and accident that the one language rule came into effect.....I'm not against controllers and pilots of the same nationality using their own language when there are no foreign aircraft on frequency... that would be churlish....but once there is a non local aircraft on frequency then the rule MUST apply....for better or worse the language of the air is English.....those of us flying today didn't decide this but like all the other rules that affect our safety... we should abide by it.