Paris Europlace, the organisation that promotes Paris as a financial centre, would no doubt pay a high price to top London in financial league tables but probably not €5 billion in losses.

Jerome Kerviel, the Societe Generale trader who engineered the massive fraud that is now being blamed for triggering Monday's market turmoil, has topped Nick Leeson, Britain's top trading rogue who only lost £800 million.

In fairness to Leeson, however, he did manage to bring down Britain's oldest bank while Kerviel appears, so far, to have only caused Societe Generale, a savage but not crippling blow.

Comparisons between Leeson and Kerviel are at first glance easy and then seem unfair. Daniel Bouton, the Societe Generale chief is no Peter Baring. That is to say, a scion of the family business, who when asked about the extraordinary "profits" booked by the lad running the derivatives business in Singapore, said he found it "pleasantly surprising".

The Barings collapse triggered a massive panic over the supervision, control and auditing of derivatives trading, a business then perceived as exotic and poorly understood, even by the most senior people in banking establishments. Leeson was at one point contributing a tenth of Baring's profit but the board barely understood the business and allowed their golden boy to act as both poacher and gamekeeper in running trading and settlement in Singapore.

The SocGen chief is cut from different cloth - the classical French breed of executive, with a civil service training, schooled at l'Ecole nationale d'administration. He worked for Alain Juppe when the latter was budget minister and joined ScoGen in 1991 as pretender, taking the reins in 1995.

SocGen has a chequered history and failed in its tilt at rival BNP. A merger of the two banks is not an unlikely scenario after this setback and is the sort of thing, engineered with a nod from the ministry of finance at rue de Bercy and a wink from the Elysee Palace, that would satisfy French honour and reduce the risk of a foreign takeover.

Still, if SocGen is leagues apart from Barings, the question remains why a former back-office clerk could so comprehensively bamboozle his employer, conduct such huge operations undetected. There is a fundamental weakness in investment banking, not so much in its regulation but in the modus operandi of institutions that require staff to be, on the one hand exemplary corporate citizens and at the same time self-centred entrepreneurs.

In other words, the ideal investment banker is both factotum and a spiv, wearing the same suit, mouthing corporate slogans while slavering after a bigger bonus. The horrible truth is that banks need guys like Nick Leeson and Jerome Kerviel to earn the biggest bucks. The factotums who rise through the ranks, do the politics and emerge as senior managers rarely have the imagination to devise clever deals nor sufficient charm or aggression to sell them to customers. The solution is to hire gutter talent but these need to be watched like hawks and no amount of scrutiny is ever sufficient.

It is 13 years since the Barings crisis and the risks of derivatives trading have been extensively analysed and dissected. We have had Jeffrey Skilling, the chief executive Enron, Sumitomo's rogue copper trader, Yasuo Hamanaka and John Rusniak, the Allied Irish Banks trader who lost $700 million. In the meantime, the deals and financial engineering has become more complex and more opaque.

In an extraordinary but frank admission earlier this month, the chief executive UBS told the bank's investors that it was not able to ascertain with any precision the extent of it potential future exposure to sub-prime losses. UBS has suffered no fraud or chicanery; it's all just too complicated. In such an environment, you can expect Nick Leeson and Jerome Kerviel to make hay.

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