Strong corporate results and a rally by banks hauled Britain's top share index into positive territory early on Thursday as investor nervousness on the Greek dent crisis eased, outweighing weakness from energy stocks.
By 0835 GMT, the FTSE 100 was up 31.71 points, or 0.6 percent higher at 5,618.32, having fallen 0.3 percent on Wednesday after a 2.6 percent tumble on Tuesday.
Senior European officials gave assurances that they were serious about helping Greece find a way out of its escalating debt crisis, helping calm investors who had been further rattled on Wednesday after Standard & Poor's Cut Spain's credit rating.
Also providing support to markets, the U.S. Federal Reserve gave an upbeat assessment of the world's largest economy and decided to keep interest rates near record lows.
"There is pain caused by the fiscal situation in Europe, but the underlying economic situation is firming up and if the newsflow is not absolutely negative, it will allow investors to focus on the underlying trends," said Gilles Moec, senior European economist at Deutsche Bank.
Energy firms were the main drag on the index with BP down 2 percent as the U.S. Coast Guard said on Wednesday that five times as much oil as previously estimated was leaking from a well beneath the site of a deadly drilling rig explosion.
Peer Royal Dutch Shell fell 0.7 percent having been boosted by strong Q1 results on Wednesday.
BG Group, however, gained 1.1 percent as its first-quarter results beat forecasts, with underlying profits up by 13 percent, and all divisions outperforming expectations.
Among a raft of other, mostly positive, company results, Unilever stood out, gaining 3.3 percent after the consumer goods giant's drive to increase volume growth paid off for the fourth quarter in a row as it beat forecasts with a rise in underlying Q1 sales.
Pay TV firm BSkyB also shone, adding 3.2 percent, as its results showed huge demand for high definition services which enabled it to add 62,000 net new customers in the third quarter of the year and increase user loyalty.
Banks were mostly higher as some reassurance on the outlook for for euro zone debt improved sentiment for the sector.
Barclays, HSBC and Standard Chartered added 0.4 to 0.6 percent. But part state-owned Royal Bank of Scotland and Lloyds Banking Group fell 1.1 and 1.5 percent respectively.
Elsewhere among financials, insurer Standard Life was also a feature on the blue chip leader board, up 1.8 percent after it said its sales rose 30 percent in the first three months of the year, well above analyst forecasts, prompting Panmure Gordon to raise its rating to "buy".
Drinks producer Diageo was also among the top FTSE 100 gainers, up 2.5 percent, as French peer Pernod Ricard lifted its full-year profit target and posted third-quarter sales above forecasts, with key markets such as the United States, Russia, as well as duty free improving.
