Robust commodity prices boosted energy and mining stocks which led a broad-based rally at the start of the third quarter, lifting Britain's top share index 1.4 percent higher early on Wednesday.
Crude rose nearly 2 percent to above $71 per barrel fuelling a rise in heavyweight energy stocks, which added most points to the index.
BP, Royal Dutch Shell, BG Group, Tullow Oil and Cairn Energy added between 1.3 and 2.3 percent.
By 0755 GMT the FTSE 100 was up 60.11 points at 4,309.32, after closing 44.82 points, or 1 percent, lower on Tuesday at 4,249.21.
The index ended up 8.2 percent on the quarter, the best such performance since the final quarter of 2003, and has gained 22.8 percent since touching a six-year low on March 9.
For a FACTBOX on European stock market performance in the first half of 2009 double click on.
The index's level is little moved since the start of May, however, and investors are awaiting more concrete evidence on the prospects for economic recovery before pushing the market substantially higher.
"We've been in a range for the last six weeks and I don't expect huge moves, people are looking at the famous shape of recovery, whether it will be "V" "W" or "L" shaped," said Teun Draaisma, equity strategist at Morgan Stanley.
Like energy stocks, miners also benefited from firmer raw materials, with metal prices stronger across the board.
Rio Tinto, Kazakhmys, Eurasian Natural Resources, Anglo American, Lonmin and BHP Billiton added between 2.1 and 4 percent.
RETAILERS RELIEF RALLY
Marks & Spencer added 3.7 percent as analysts nudged up their full-year profit forecasts for the iconic high street retailer after it posted a smaller than expected decline in first-quarter underlying sales.
Peer Next also gained, up 3.3 percent.
Banks were broadly higher, as the risk sensitive stocks responded well to increased investor confidence.
Barclays, HSBC, Standard Chartered, Royal Bank of Scotland and Lloyds Banking Group added 0.5-2.3 percent.
Investors will look to the UK June manufacturing sector PMI report, due at 0828 GMT, to provide further clues as to the health of the domestic economy.
U.S. June ISM data will be a focus later in the session, together with May U.S. pending home sales numbers, and the June ADP National Employment report, a precursor to Thursday's crucial U.S. jobs report.
Man Group was the biggest faller among just a handful of stocks in the red, down 4.8 percent after going ex-dividend. Alliance Trust, and Compass Group also lost their payout attractions denting their performance.
