Fresh attempts by the European Central Bank to stimulate the region's moribund economy boosted shares and left the euro sharply lower.
The FTSE 100 Index broke through the 6,900 barrier for the first time in 14 years before a sharp slide for shares in oil giant BP caused the top flight to close just 4.4 points higher at 6878.
Markets in Paris and Frankfurt were up by around one per cent after the ECB slashed eurozone interest rates from 0.15 per cent to just 0.05 per cent .
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It cut the overnight deposit rate for lenders that hold money with it to minus 0.2 per cent.
The latest rates cuts weakened the euro by one per cent against the pound, which stood at 1.26 against the single currency.
Sterling was slightly lower against the US dollar at 1.64 after the Bank of England opted to keep interest rates at 0.5 per cent for another month.
Elsewhere in a busy session for financial markets, BP shares dived after a US judge found the company grossly negligent over the Gulf of Mexico disaster, leaving it facing civil fines of up to 18 billion US dollars (£11 billion).
The ruling under the Clean Water Act caused BP's shares to slump six per cent, or 28.75p down to 455p, and acted as a drag on the performance of the FTSE 100.
Standard Life was the biggest riser in the top flight, lifting by as much as 10 per cent.
This came after the Edinburgh-based pensions giant boosted its popularity among its army of private shareholders by announcing that it would return £1.75 billion to investors following the sale of its Canadian business.
The capital return to investors is equivalent to 73p per share. Shares closed eight per cent higher, up 31.1p to 417.2p.
Also on the up was SuperGroup, the firm behind the Superdry fashion brand.
Its trading figures for the first quarter from April 27 to July 26 showed revenues up 15.9 per cent to £87m.
Shares lifted almost 14 per cent, or 145p, to 1191p.
Other stocks making progress on the FTSE 250 Index included transport operator Go-Ahead, after it posted a 44 per cent increase in full-year pre-tax profits to £91.2m.
Shares climbed 72p to 2345p as the company announced the first hike in its full-year dividend payment in six years.
Among the FTSE 100 fallers, British Gas owner Centrica was lower after it said the temporary shutdown of two nuclear plants in which it has a 20 per cent stake will have a bigger than expected impact on its earnings.
The biggest FTSE 100 risers were Standard Life up 31.1p at 417.2p, SABMiller up 102.5p at 3460p, Carnival up 68p at 2358p and Coca-Cola up 38p at 1469p.
The biggest FTSE 100 fallers were BP down 28.75p at 455p, Fresnillo down 22.5p at 909.5p, Hargreaves Lansdown down 24p at 1049p.
Sage Group's shares were down 5.8p at 395.7p.