Like Hollywood marriages, partnerships between senior bankers are often short-lived and unhappy affairs in which one party agrees to suppress their ambition for a brief period of time, normally followed by a swift and highly public divorce.

In a world where precedents include the breakups of Stuart Gulliver and John Studzinski at HSBC, and Oswald Grübel and John Mack at Credit Suisse, Bill Winters and Steve Black's co-headship of JP Morgan's investment bank stood out as the shining example of what could happen when two people with complementary skills were put to work alongside one another.