The share prices of some the UK's best-known companies appeared to fall as much as 99 per cent today, after the London Stock Exchange (LSE) updated its tech over the weekend.
The LSE upgraded its trading technology over the weekend and City sources pointed to this being the most likely cause of the problems.
The problems were due to systems reporting trades in pounds rather than pence, following the tech update, which allowed traders to post trades in different currencies.
A spokesperson for the LSE insisted the exchange's systems are working correctly and the dramatic price movements were the result of data vendors displaying prices incorrectly.
Shares in ailing contractor Carillion fell from more than 20p to 0.2p on at least six separate occasions between 10am and just after 11am today.
Meanwhile, ITV shares languished at around 1.5p for two minutes, around one-hundredth of the FTSE 100 firm's normal price.
Today's ITV share price
The BBC was forced into apologising to readers on its online blog, saying the LSE was experiencing "technical issues that will not be resolved until tonight at the earliest".