FTSE sheds 20% in a week
The latest fall for London's shares means the FTSE 100 Index has now shed about 20% of its value this week - its worst week since Black Monday in 1987.
Co-ordinated interest rate cuts across the world and this week's efforts by the UK Government to bolster UK banks failed to reassure panicked investors.
Banks and insurers were the hardest hit with Royal Bank of Scotland plunging 25% and HBOS sinking 19%.