US shares shed gains after a global stock market rally.Read more
The blue-chip index closed down 4.05%, after losing 214.32 points, at 5,080.58.
The wider FTSE 250 lost 6.58%, or 916.69 points, to fall to 13,008.19
The blue-chip index has ended the day up 2.79%, or 143.82 points, at 5,294.90.
But the mid-cap FTSE 250 index closed down 424.78 points, or 2.96%, at 13,924.
Let's have a look at the markets. The FTSE 100 is holding steady above the 5,000 level.
It's at 5,070.50, a fall of 80.58 points or 1.56% on the day.
The wider FTSE250 index is quite a lot worse off.
It's at 13,783.50, a fall of 566.25 points or 3.95%.
Well the early morning rally didn't last long. After opening higher the FTSE 100 has resumed its downward path and is now down 1.6% at 5,069.50.
The FTSE 250 index is also lower, down 2.4% at 14,003.12.
After Monday's hefty falls on the world's stock markets, London's FTSE 100 index has opened higher.
In the first few minutes of trade the index is up 99.29 points, or 1.9%, at 5,250.37.
The FTSE 250 index is up 273.26 points, or 1.9%, at 14,623.01.
A dead cat bounce is when share prices benefit from a brief recovery in the midst of a plunge.
Is that what's happening today?
Rabobank stretegist Michael Every thinks so.
"We sure seem to be witnessing a classic dead cat bounce with the Stoxx 600 up about 3.5% and all regional bourses experiencing a positive to very positive open, like in London, with the FTSE up 5%," he says.
"It’s been a black week already – and even if today sees another dead bat bounce, it’s hard to see where any real structural relief is going to come from until we get a virus vaccine."
It's a mixed picture on the FTSE 250 index of smaller, more UK-focused firms.
The biggest winner is Finablr, which owns travel money company Travelex, which was brought to its knees by a cyber attack that all but paralysed the firm earlier this year.
Its services have since been restored but yesterday Finablr's share price plunged by more than 60% after the firm said it was taking urgent steps to assess its "liquidity and cashflow position".
Its shares have bounced this morning and are currently up over 50%.
There was no such luck for Cineworld investors. Shares are down around 14% after the firm said yesterday that coronavirus could threaten its ability to keep trading.