Rogue traders can get banks into trouble because top executives can't tell their assets from their elbows

How much rope to give employees? Enough to hang themselves? Probably. Enough to string up the entire organisation? Hmmm. That's taking the light management touch a little too far.

John Rusnak, a 37-year-old middle-ranking currency trader from an unpretentious Baltimore suburb, used his freedom to sow mayhem for the best part of a year. At the end of his spree, he had lost his bank - a subsidiary of Allied Irish Banks - $750m on betting the yen against the dollar.

He was not a master of the universe. Rusnak was half of a two-man team hundreds of miles from Wall Street. His job was to identify minuscule discrepancies in the price of currency between markets and make a tiny profit by buying in one market and selling in another. It is called arbitrage and is not quite as straightforward as it sounds, because the different markets could be cash markets, futures markets and options markets (where traders deal in the right to buy and sell a currency at a later date at a predetermined price). Even so, in its conventional form, the work is dull and predictable.

In other words, Rusnak was a train-spotter, but one who wanted to drive the engine at full throttle. He made huge bets that the value of the yen would rise. It did not. So Rusnak created imaginary profits on phoney options deals to offset his real and enormous losses.

Had he kept going, he could have bankrupted Ireland's biggest bank. As luck would have it, Rusnak's colleagues got a whiff that something was awry a few weeks ago, when he started asking for surprisingly large cash sums (which he needed so as not to welsh on the genuine bad deals). Among the dematerialised, computerised cacophony of digitised information, at least companies can still count on cashflows to tell them the truth about what is going on.

However, AIB should have spotted that something was up much earlier. Banks are supposed to have highly sensitive and sophisticated systems for keeping an eye on what their employees are doing with their precious capital. If AIB had these monitoring systems, which it claims it did, then its executives failed to read the instruction manual.

But it would be foolish to join in the City stereotyping and assume that AIB is an Irish exception to the rule that banks are, on the whole, masters of their destiny. The truth is that a whole generation of executives at the apex of the global financial system have only a tenuous understanding of how their people generate income.

There is nothing terribly new or particularly complex about currency options, compared with the much more arcane "derivative" products and services that even high street banks dabble in. But I would make an unhedged bet that there is not a single big British bank whose chief executive can price a currency option without coaching and support from assorted flunkeys.

For some years, senior bankers have made a virtue of their ignorance. What mattered, they said, was that they were adept (ahem) at general management, or at recruiting and motivating those with the technical skills. Look at Tesco. Do we think it will go bust if its head has never worked on the tills, stocked the shelves or - more germanely - designed a stock- control system? But trading in risk, which is what banks do, is different from selling bananas. A wrong judgement can be calamitous.

In the past few days, chief executives of every big bank have been sending out anxious requests to subordinates for verification that they do not employ a Rusnak. If any of the reassuring answers were provided by Rusnak's clever evil twin, how would any of them know?

Whatever Rusnak's faults, slacking on the job was not one of them. If anything, AIB wishes he had been rather less busy. And this Stakhanovite took his work home with him: the FBI is desperate to get its hands on the family PC before the hard disk is sterilised.

He is proof, if it were needed, that working more is not necessarily working better - though the CBI won't buy it. It is an act of absolute faith for the business lobby that disaster looms for the British economy if employees are banned from contracting to work more than 48 hours each week.

The CBI appears to have won over the Department of Trade and Industry, because I am told that ministers are minded to apply for renewal of the UK's partial opt-out from the European Union's working time directive, which sets this ceiling on the working week everywhere else in Europe.

I am torn about all this. If the government accepted the restriction, the much-needed drive to liberalise EU markets in general might lose momentum. There is also a freedom issue here: the right to work more or less is not completely trivial.

However, there is a horrible, competitive, macho culture in the UK of working around the clock, to the detriment of health, sanity and family well-being.

So here is my compromise, which has the merit of being redistributive. The 48-hour ceiling should apply only to those earning less than £100,000 a year. There would be a transfer of valuable leisure time from high earners to low earners. And, in the spirit of good old Croslandite egalitarianism, there could be a de facto leisure tax on those earning more than £100,000: members of the CBI earning above the threshold would be locked in their offices until they had worked ten hours a day. That'll learn 'em.

Robert Peston is editorial director of QUEST ,; e-mail