With a buyout in the bag, David Mayhew could be expected to walk away from the City and spend more time pursuing passions such as fly-fishing and his herd of pedigree cattle. He is, after all, 69. But he is widely expected to want to carry on at Cazenove, where he has worked for 40 years, and that is likely to be welcomed by JP Morgan.

While some accuse Mr Mayhew, the chairman, of not allowing young talent to get a decent foothold in Cazenove’s hierarchy, it is widely recognised that the Old Etonian has perhaps the best contacts book in the City. He belongs to an exclusive club of the City’s most senior bankers and lawyers who still pull the strings in many boardrooms.

His counsel is also valued by governments. When Royal Bank of Scotland and HBOS were on the verge of collapse last September, Mr Mayhew topped the list of advisers to whom officials turned.

His career has not been without controversy. He was charged in the Guinness share support scandal of the late 1980s, but the case collapsed. Cazenove made clear that it would stand by him.

Widely credited with charm and discretion, Mr Mayhew has worked on some of the City’s most notable deals, including the merger of Halifax and RBS in 2001.

After Eton, he went straight into stockbroking at Panmure Gordon. He joined Cazenove in 1969, becoming a partner in 1972 and chairman in 2001. He is regularly to be seen outside the offices of Cazenove at Moorgate enjoying a cigarette.

The embodiment of the City’s old guard, Mr Mayhew has, through a series of unorthodox manoeuvres, preserved Cazenove as one of the last remaining independent houses in the City.

Despite its impending full integration into JP Morgan, most believe that the Cazenove culture will survive.