The FTSE 100 held on to gains of around 200 points today amid hopes for Barack Obama's stimulus package for the US economy.
The US president-elect has vowed to spend hundreds of billions of dollars on a public works campaign, creating some 2.5 million jobs, to lift the US out of recession.
There are also hopes that the US car industry will receive a $15bn bailout.
Earlier the FTSE 100 rode to a high of 4300.95 – more than 250 points up on Friday night's close and its best level for four weeks.
At that point the blue-chip index wiped out last week's deficit of 238.64 points.
But soon after midday it slipped to 4246.18, still a gain of 196.81.
All but three of London's 100 leading shares were in positive territory.
Financial stocks were strong, as are the miners and oil companies, thanks to rising commodity prices.
Prudential headed the list of gainers, up 14.25% to 333.25p.
Insurer Old Mutual rose more than 11% to 48p, while Barclays, the high-street bank that has shunned government funding, was up more than 9% at 150.9p.
