The objections raised to Marks and Spencer’s surprise decision to appoint Sir Stuart Rose, chief executive, as the British retailer’s executive chairman must look strange seen from the US, where it is the norm for a company’s top executive to hold the roles of chairman and chief executive. As noted here last year, no less an authority than Alan Greenspan has concluded that “CEO control and the authoritarianism it breeds are probably the only way to run an enterprise successfully”.

But since 2003, when Britain introduced its combined code on corporate governance, the number of large listed groups that give their chief executive the title of chairman has dwindled. One exception in the FTSE 100 blue-chip index is Carnival, the cruise line, whose long-standing chairman and chief executive is Micky Arison. He railed against the UK code’s strong recommendation to split the roles when Carnival took over P&O Princess Cruises in 2003. Carnival is an exception in other ways: a dual-listed company, run out of Miami, it boasts that it is the only group with a place in the FTSE 100 and the S&P 500.