The FTSE 100 index rose 0.4%, boosted by heavyweight miners such as Glencore and Anglo American after U.S. President Donald Trump agreed to delay increasing tariffs on $250 billion worth of Chinese imports.

The mid-cap index added 0.2% by 0809 GMT to scale its highest level in nearly a year. The index has gained more than 3% so far this month as fears of a no-deal Brexit receded.

"Investors are lapping up any sign of positivity and any excuse to get pushed up the risk curve," Markets.com analyst Neil Wilson said.

In news-driven moves, BAT advanced 2.8% after the world's second largest tobacco company by sales said it planned to lay off employees globally and focus on newer smoking options such as e-cigarettes. Its shares were the single biggest boost on the main index.

Morrisons climbed 3% after Britain's No.4 grocer posted a 5.3% rise in first-half pretax profit that surpassed analysts' forecasts and announced a special dividend.

Meanwhile, Premier Inn owner Whitbread slipped 3% and Intercontinental Hotel 2.2% after JPMorgan downgraded the stocks to 'underweight', citing uncertainty in the macroeconomic environment.

Markets participants were also awaiting the European Central Bank's meeting later on Thursday to see how far policymakers will go to support a flagging eurozone economy.

"Investors are after not only a rate cut, but a new round of the central bank's asset purchase programme as well. Anything less than that may leave a bitter taste in the market's mouth," Spreadex analyst Connor Campbell said.

Inkjet tech company XAAR jumped 25% after it agreed to sell 20% of its holding in Xaar 3D to U.S. company Stratasys  for $10 million.

Shares in small-cap N Brown skidded as much as 10% to their lowest since April after the fashion retailer said it would set aside another 20-30 million pounds in provisions relating to the mis-selling of payment protection insurance.