The FTSE 100 index closed up 30.46 points or 0.5 per cent at 5,891.21, its best performance since June 2008, despite trading which analysts described as “lacklustre”.
In contrast, the mid-market FTSE250 hit three year high, closing at 11,380.
BP was the biggest FTSE100 riser, closing up 3.2 per cent on the back of its sale of Pakistani oil fields to United Energy Group for $775m (£490m).
Serco, BAE Systems and AstraZeneca all added about three per cent over the day.
Chipmaker Imagination Technologies was the FTSE250’s top performer, after announcing it had bought 3D graphic firm Caustic Graphics for $27m to bring 3D graphics to mobile phones.
But Costa Coffee and Premier Inn owner Whitbread failed to convince markets on its results, falling 2.79 per cent despite pushing Costa’s sales up 13.6 per cent.
“It’s been a pretty slow session for UK markets,” said CMC Markets analyst Michael Hewson.
The LSE’s afternoon trading was boosted by positive US economic data, which supported views of a growing fourth-quarter recovery.
“US markets opened fairly flat but with a slight upward bias as US economic data showed that both retail sales and producer prices rose a bit more than expected in November,” Hewson said.
By 4pm UK time the US markets saw a continued strong run, with the Dow Jones Industrial Average up 48 to 11,477; the broad-based S&P 500 up 1.12 to 1,241, and the Nasdaq up 2.81 to 2727.
Traders remained positive about Wednesday’s outlook.
“Tomorrow holds potential for the FTSE to break through the 5900-level if UK unemployment and US CPI figures indicate steady recovery, said Chris Purdy, a trader at spread betting firm Spreadex.