Michel Wurth, chief financial officer of Arcelor, the European industrial group that produces 5% of the world's steel, is hopping mad. Or, at least, as hopping mad as an urbane businessman can get when he is sitting down.

I want to ask him about making mergers work – something that Wurth, as one of the architects of a complex three-way merger, is well qualified to discuss – but he is furious about the fact that Standard & Poor's (S&P) has just put Arcelor on credit watch, along with nine other European companies.