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UK indexes start trading after delay

Trade in the UK's blue chip FTSE 100 and midcap stock indexes has started after a delay because of a technical glitch in what was the longest outage at one of the world's top bourses in eight years.

The outage was affecting hundreds of shares in some of the UK's largest companies, including Shell, Unilever and HSBC and BHP Group, worth a total of $US2.8 trillion ($A4.1 trillion).

This is the second outage at the LSE, which handles about 5 billion pounds ($A9 billion) worth of volume each day, in just over a year.

In June 2018, the opening auction was delayed due to a technical fault, but trading resumed after an hour.

Prior to that, the market was shut until lunchtime one day in February 2011.

Reuters News' parent Thomson Reuters holds a 45 per cent stake in financial data and news provider Refinitiv, which is being bought out by the LSE. Thomson Reuters will own 15 per cent in LSE after the proposed deal closes.