Years of planning and frenzied activity to get systems ready have lead banks and European Union officials to be sanguine about the prospects for the euro's launch.

Trading could grind to a halt if systems fail

But someone, somewhere is bound to have got it wrong. It is inconceivable that the introduction of the euro, which promises to transform the world's currency markets, will not pass without at least a few technical hitches.

At best the introduction of the euro will lead to minor teething troubles at some finance houses. At worst a huge number of trades could fail, causing chaos across the world's financial markets.

Chain reaction

Up to now banks have only tested their own systems in isolation. But to operate successfully they rely on fellow members of the financial community. If one link in the chain is broken, deals could fail to be completed.

Cap Gemini, one of Europe's leading computer consultancies, has warned that up to 40% of all euro transactions in the next week could be delayed due to computer problems at financial institutions.

This could severely disrupt currency and stock markets and leave banks with the headache of clearing a backlog of deals. Cap Gemini believes that extra staff will be needed after the euro starts trading to help counter the expected problems.

Costly mistakes

David Clementi, deputy governor of the Bank of England, had warned that mistakes are inevitable and could prove very costly.

If the experience of the Big Bang of 1986, when the UK stock market embraced electronic screen based trading, is anything to go by the introduction of the euro could cause severe disruption.

Hundreds of thousands of bank employees who have had their festive break ruined were hoping to celebrate the New Year after the launch of the euro on 4 January. But they may have to wait a bit longer to pop the champagne corks.