By tapping in the wrong instructions, the German-based employee informed the trading floor that someone wanted to sell 130,000 German bond futures contracts worth £11.5bn.

The contracts are more usually sold in bundles of 10,000 at most.

The news set off panic buying with many seasoned traders thinking it was a "Rio trade", where somebody bets their bank or similar financial institution in an effort to recover losses and if that fails they buy a one-way ticket to Brazil.

'Easily confused'

The trader's employers are now obliged under contract to fulfil their purchasing commitment by buying bond futures contracts on the open market.

Many traders were astonished that the trainee was able to complete his transaction without the size of the deal attracting attention from his superiors.

The dealing program for the Eurex German electronic exchange where most German bond futures contracts are traded is reportedly very easy to confuse with the trading simulation software package.