Update: The FTSE 100 was spurred higher by a strong open for US markets, after Federal Reserve chair Janet Yellen adopted a dovish tone in her statement before the US congress.
In prepared remarks released ahead of her appearance, Yellen said interest rates 'would not have to rise all that much further' to reach a 'neutral' level, adding that the Fed would be 'monitoring inflation developments closely', with the pace of price rises below the central bank's 2% target.
Luke Bartholomew, investment strategist at Aberdeen Asset Management, said Yellen's statement could make a another US interest rate hike this year less likely.
'The big mystery surrounding the US economy has been why low unemployment hasn't translated into stronger wage and price growth,' he said.
'Up to now, the Fed has steadfastly maintained that inflation will pick up eventually. But Yellen's statement today reveals the Fed isn't as sure about inflation as they led us to believe.'
The prospect of US rates remaining low for longer buoyed stock markets across the pond, with the S&P 500 and Dow Jones opening 0.7% higher.
That gave the FTSE 100 an extra spurt, with the UK blue-chip index building on the morning's gains to trade 85 points, or 1.2%, higher at 7,415.
But Royal Bank of Scotland (RBS) slid into the red, down 1.4% at 253p, after agreeing a larger-than-expected £4.2 billion settlement with the US Federal Housing Finance Agency over the sale of mortgage-backed securities in the run-up to the financial crisis.
(11:35) Pearson and Carillion slump deepens
Miners and oil stocks have driven the FTSE 100 higher but educational publisher Pearson (PSON) has found itself at the bottom of the index for a second day.
The UK blue-chip index rose 71 points, or 1%, to 7,401, with miners leading the way after a rise in the copper price, as a rapid build-up in inventories halted and Chilean workers voted to strike, sparking supply concerns.
Burberry (BRBY) also found itself among the leaders, up 2.7% at £16.23 after encouraging results from the luxury goods maker.
'Burberry shares are reflecting palpable relief this morning after an unexpectedly solid advance in first quarter comparable sales growth and the most promising underlying trend in China for at least three years,' said Ken Odeluga, market analyst at City Index.
Languishing towards the bottom of the index for a second day was educational publisher Pearson, as investors continued to sell off the stock amid disappointment at management's . Down 5% at 622.,5p, the stock has now fallen 10% over the last two sessions.
The biggest FTSE 100 faller was Micro Focus International (MCRO), down 6.4% at £20.57 as the software company's full-year results missed expectations.
Among 'mid cap' stocks, Carillion's (CLLN) woes deepened, with the shares down a further 9.9% at 70.2p. The shares have now lost 63% this week, after the infrastructure and construction firm issued a profit warning on Monday, raising fears of a big rights issue.
The star performer of the day was 'small cap' stock Premier Oil (PMO), which soared 28.1% to 59.3p, as the explorer announced a 'world class' oil discovery in offshore Mexico.