The c-suite is a lonely place. A chief executive in need of trusted advice traditionally turns to a City-dwelling species known as the corporate broker, ideally a Jeeves-like figure who saves our bumbling hero from disaster. Need to raise money? A good idea to explain why, the broker will suggest. Tempted to introduce a lavish new compensation scheme? Perhaps not quite the best moment. A good broker makes a market in the shares, knows the investor register like the back of his hand, publishes respectable equity research and provides reasonably selfless corporate advice. He can be the chief executive’s eyes and ears, able to spare him the embarrassment of a rebuff from his own shareholders.

Such relationships are in disarray, with perhaps half the UK’s largest companies expected to review their corporate broking arrangements. Turmoil at several of the biggest brokers – with Dresdner, for example, exiting the market and Merill Lynch and UBS experiencing instability – is creating the opportunity for the biggest shift in market share since 1986. The big winners so far are JPMorgan Cazenove, which has pushed up its share of the FTSE 100 to 37 from 34 in a little over a year, and Investec, now broker to 22 FTSE 250 companies, up from eight.