London’s blue-chip completed the fight back it was making at lunch to swing to a gain as the afternoon wore on.
Chris Beauchamp at IG said: “Ahead of what looks like the most vital Fed meeting in years, the best thing for markets to do would be simply to sit still and wait for Thursday afternoon.
“With that being impossible, they have opted for the second choice, namely running around in circles.”
The UK’s main index was boosted by a positive start to the day on Wall Street, where, having been poised to open lower the benchmark Dow Jones rose 56 points, at 16,428, the broader S&P500 was up six at 1,959 and the Nasdaq gained ten to 4,816.
With all data this week potentially affecting the Federal Reserve’s interest rate decision on Thursday, the key question is whether the US economy is robust enough to weather a rate rise.
Retail sales figures did little to solve this mystery, rising modestly in August by 0.2%.
Dennis de Jong at forex broker UFX said: “even slight improvement is still a positive, especially considering weak inflation recently.”
The data had a knock on effect in Europe, where the French Cac40 was 1.4% higher to 4,581 and the German Dax rose 83 points to 10,215.
In the UK, the FTSE 100 ended the day 53 points to the good at 6,137 with ARM Holdings (LON:ARM) leading the charge.
The chipmaker said its third quarter trading and operating costs are broadly in line with guidance.
Earlier this week, major customer Apple said initial sales of its newly introduced iPhone 6S are likely to beat the record set last year. Shares climbed 3.4% to 980p.
Conversely, B&Q owner Kingfisher (LON:KGF) was languishing at the bottom of the index, down 4% to 345p as it reported higher half-year sales but lower profits and said it was on track to close about 60 stores.
In the small cap space, Teathers Financial (LON:TEA) climbed as it said Its technology platform will be used to power a crowd equity app being launched by Shard Capital Partners.
It is Teathers’ first commercial agreement and will be free to download on iTunes, Google Play and Android. Shares rocketed almost 20% to 3.1p.
Elsewhere, Mosman Oil & Gas (LON:MSMN) shot higher as the company moved STEP closer to acquisition with a royalty agreement worth NZ$4mln.
The company recently agreed to acquire STEP - the South Taranaki Energy Project - for NZ$10mln, and shares jumped 27% to 8.2p.
Conversely, the tough oil & gas market hit Hydrogen Group (LON:HYDG), which reported widening pre-tax losses of £1.9mln from £1.1mln in its interim results. It has also scrapped its dividend.
Cost-cutting measures are expected to take effect in the second half, the company said, but it couldn’t stop shares falling 19% to 43p.