On a surge in French mergers and acquisitions action this year, two venerable French banks have surfed their way confidently to the upper echelons of M&A the league tables. The question now is, can they stay there?

With a spate of multibillion euro deals, France's share of European M&A has doubled from its traditional 15% to 33% in the year to April 23, according to data provider Dealogic.