The London Stock Exchange was forced to suspend trading in several symbols this morning after a problem with invalid data.
At around 10.00am the exchange put out a notice confirming an "issue" with its trading system meant one in twelve FTSE100 instruments were unavailable.
The bourse says the problem - which it stresses was not related to underlying technology - affected customers inputting orders into certain stocks. As a result it asked clients to refrain from entering orders in those securities.
About an hour later the affected securities were bought back up once the backlog of data was cleared. All the securities resumed trading as normal just after 11.30.
Only a "small number" of securities were affected and the rest of the market and the Italian market was unaffected, says a spokesman.