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The fly in your photos is certainly a Tachina - a similar genus would be Peleteria but your photos don't show any "Peleteria bristles" on the lower part of the parafacial. Nowickia is also an alternative but the legs are jet-black (not brown, as in yours) and the dark patches tend to be very much blacker.

In the UK it would be Tachina fera but to go further with your French specimen would require an expert familiar with the European fauna - and possibly a specimen. I have keyed a few T. magnicornis so if you want to send a specimen to me I'd be happy to key it through :)