Up to speed in French (2,4)

I think it could be either:

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2,4

au fait

(Other definitions for au fait that I've seen before include "Well acquainted with, knowledgeable about" , "Expert" , "Conversant with or knowledgeable about - in France" , "Well-acquainted (with)" , "Conversant or well acquainted with - in France" .)

I've seen this clue in The Guardian.

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