Britain's top share index rose towards a 4-1/2 month high on Tuesday, boosted by energy stocks as BP's results beat earnings expectations.
The blue-chip FTSE 100 index ended up 1.3 percent at 6,871.80 points, near its highest level since September 2014.
Intertek, whose services include testing products to make sure they comply with safety standards, rose 6.5 percent - the best-performing FTSE 100 stock in percentage terms - as investors welcomed its acquisition of Adelaide Inspection Services.
Oil major BP gained 2.8 percent after it beat quarterly profit expectations despite taking a $3.6 billion impairment charge in the face of low oil prices.
Oil company Afren, which is in the FTSE 250 mid-cap index, advanced 18.4 percent on prospects of a deal with Nigerian peer Seplat.
Energy stocks further benefited as the oil price rallied on Tuesday, extending a rebound after falling near six-year lows last month.
"I am very impressed by how this market is breaking to the upside. The respite in the slide of the oil price is giving us some breathing space," said Beaufort Securities' sales trader Basil Petrides.
However, Aberdeen Asset Management fell 3.4 percent after reporting a small drop in funds under management.
The FTSE hit a peak of 6,904.86 points at the start of September, its highest level since early 2000, but then lost ground towards the end of 2014.
(By Sudip Kar-Gupta; Additional reporting by Alistair Smout; Editing by Mark Trevelyan)