The FTSE 100 had begun a fightback from last losses sparked by the standoff between the US and North Korea.
The UK blue-chip index rose 42 points, or 0.6%, to 7,351, clawing back some of the losses incurred last week as global markets sank.
The FTSE 100 fell 2.7% last week amid escalating tensions between the US and North Korea. US president Donald Trump first threatened to unleash 'fire and fury', later claiming that 'maybe that statement wasn't tough enough'.
North Korea meanwhile outlined plans to launch missiles aimed at the waters off the coast of the US pacific territory of Guam, saying the exercise would be ready to await orders from leader Kim Jong-un by the middle of the month.
Deutsche Bank's Jim Reid said the sell-off had so far been 'measured'. 'It's just that in the context of very, very calm markets recently it's still been a bit of a shock,' he said, suggesting that thin trading levels in the August summer lull could be party responsible.
He pointed to a Wall Street Journal study of previous North Korea flare-ups, where the impact on markets had been minimal, but added that Trump's unpredictability was adding to investors' nervousness.
'With his popularity low and legislative failures hurting then it's possible to envisage a scenario where he reacts more aggressively than earlier presidents,' he said.
Banks, the hardest hit by last week's sell-off, were among the risers as the FTSE 100 recovered. Standard Chartered (STAN) rose 3% to 776.4p, HSBC (HSBA) was up 1.3% at 746.1p and Royal Bank of Scotland (RBS) added 1.2% to 260.1p.
TUI (TUIT) was meanwhile the biggest riser on the index, up 4.3% at £12.84 after an upgrade from analysts at Credit Suisse.