Leaving school at 17 to become a lowly clerk on the floor of the London Stock Exchange was not quite what Jeremy Isaacs' parents had in mind for him.

Having grown up in a well-heeled north London family and been educated at public school, the young man was expected to do something a little more conventional.

Now that he is chief executive of Lehman Brothers in Europe with additional responsibility for Asia, they may feel differently. "My family thought I had lost my marbles," says Mr Isaacs.

Joining Smith Brothers as a clerk was even more lowly than being a blue-button, or apprentice dealer, which he achieved a year later. "Now I suppose they can see I was right."

At 36, Mr Isaacs is thought to be the youngest banker in such a senior position and is already one year into the job.

As a member of Lehman Brothers' executive committee, he is also one of the most senior Britons on Wall Street, alongside such people as Deryck Maughan and Michael Carpenter at Citigroup.

He finds himself in charge of Lehman's operations in Europe at an important time for the bank and for the industry.

As investment banks have merged furiously this year in pursuit of scale, Lehman has found itself a silent participant, looking at a number of possibilities but so far rejecting them all.

Mr Isaacs is adamant that - contrary to some analysts' predictions - Lehman, which sits in the middle tier of global investment banks, will continue to be the master of its own destiny and is more likely to be a buyer than to be bought.

Either way, Lehman seems certain to be near the centre of industry activity in 2001, even if it continues to expand only as it has done over the past 12 months in Europe. Mr Isaacs believes his age is completely irrelevant. "The world has shifted - it is about ability levels," he says. In this respect, Mr Isaacs is totemic of the change that has taken place in investment banking, and the City of London especially, over the past decade.

As relationship banking has faded and products have become more complex and execution more critical, the young Turks are in command.

Grey hair and a wizened face no longer spell experience in an age where power is derived from acquiring the latest information.

Mr Isaacs oozes that "can-do" confidence that makes clients feel no structure is too complex.

Part of that was developed in the open-outcry environment of the stock exchange floor during the 1980s, when he was on the London Traded Options Market.

"The pit environment was one that really suited my personality. If you were comfortable screaming and shouting it was great fun."

He spent seven years at Smith Brothers, working under Michael Marks, with whom he is still friends. Mr Marks, who was also once a blue-button, is now chairman of Merrill Lynch in Europe.

Mr Isaacs then had a brief spell at Kleinwort Benson, which he did not find entrepreneurial enough, and decided he needed to sharpen his skills. Impressed by Goldman Sachs, he moved there in 1989 to help set up the firm's derivatives desk in London.

"In the beginning I had maths lessons twice a week," he says. "It was like going back to school again. But I'm glad I recognised that on wit alone you couldn't get by. You need formal training."

Seven years later Dick Fuld, chairman of Lehman, was courting him over breakfast in London's Howard Hotel, and he moved across to help manage the European equity business.

But for all the time he has spent working for US banks, Mr Isaacs says: "I'm very much a Londoner." He still lives near his family and friends in north London.