The details of what looks like the fraud of the decade are only just beginning to come out. There are many unanswered questions, not least whether the unnamed rogue trader profited personally at all or, indeed, whether the gendarmerie has been called in. SocGen will not amplify on its statement until a press conference later this morning.

However, the parallels with Nick Leeson and Barings are already being drawn. Like Mr Leeson, the unnamed trader was betting on stock market indices. Mr Leeson took positions on Japan's main index, the Nikkei, while the Paris trader dealt in derivatives linked to European market indices. Both, in essence, were taking big bets on the direction of markets.

And like Mr Leeson, the trader had a strong background in the bank's middle office, the unglamorous but essential part of the securities industry where trades are processed. Both, it appears, had the experience and expertise to cover their tracks — temporarily, anyway.

After Barings, every securities house in the world took a long, hard look at their controls and procedures, especially the way the back and middle offices are supposed to catch out traders breaching trading limits. That was 12 years ago and memories are short in financial markets. After SocGen, the same lessons will have to be learnt all over again.

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