London's FTSE 100 Index jumped higher as Wall Street rebounded after its recent tech sell-off, but sterling dropped in another painful session over no-deal Brexit concerns.

The top tier closed 1.4 per cent or 82.5 points higher at 6012.8 thanks to a strong early session in America as bargain hunters piled in to pick up cheaper tech stocks after Tuesday's heavy declines.

The Dow Jones Industrial Average was 1.9% higher at the time of close in London, but experts saw little firm reason behind sudden halt to the tech rout.

Tech titans Apple, Amazon and Microsoft all made solid gains in the bounce-back following three sessions of declines.

David Madden, market analyst at CMC Markets, said: "There hasn't been any major positive news in the past 24 hours, but the turnaround in sentiment in the US tech sector has influenced the mood in Europe.

"Recently, any big sell-offs in Europe have been driven by the moves in the US tech sector, so now that some calm has been restored over there, things are on the up here."

There were yet more falls for the pound amid mounting worries over Boris Johnson's controversial plans to override parts of his Brexit deal with the EU.

Sterling's woes ramped up as Mr Johnson faced angry MPs over his Brexit negotiation move at Prime Minister's Questions, sending the pound plunging by another 2.1% at one stage to a six-week low of just under 1.29 US dollars.

The pound later clawed back some lost ground to stand 1.2% lower at 1.30 US dollars and 1.2% down at 1.10 euros.

Among stocks, drugs giant AstraZeneca was in sharp focus after it paused trials of its Covid-19 vaccine under development with Oxford University due to a reported side-effect in a patient in the UK.

But the group's shares shook off the set back, rising 0.5% or 38p to 8,386p.

Multinational stocks on the top tier also fared well thanks to the weakness of the pound, with those that make the bulk of their revenues overseas enjoying gains.

This helped plant-hire group Ashtead rise 5% or 144p to 2844p, with cigarette giants British American Tobacco and Imperial Brands up 4% or 93.5p to 2668.5p and 34p to 1360.5p respectively.

Elsewhere, Tullow Oil shares were hit hard, plunging 17% after the energy company warned of a potential liquidity shortfall at its first-half results.

The group closed down 3.4p at 16p as it also posted a more than $1.4 billion (£1.1bn) first-half loss.

Airlines dropped into the red once again as carriers were forced to announce further capacity cuts following the latest additions to the quarantine list.

British Airways owner International Airlines Group was 3% or 7.4p lower at 200.4p, with FTSE 250 budget rival easyJet falling 2%, or 12.6p to 584.8p.

And recovering oil prices gave a fillip to BP and Royal Dutch Shell – ahead 18p at 1041.6p and 3.75p at 262.25p respectively - as the cost of Brent crude jumped 4% to 41.38 US dollars a barrel.

The biggest FTSE 100 risers were BT Group ahead 5.9p at 110, Ashtead up 144p at 2844p, Unilever 175p stronger at 4743p and British American Tobacco 93.5p higher at 2668.5p.

The biggest FTSE 100 fallers were Rolls-Royce down 8.2p at 210.7p, IAG off 7.4p at 200.4p, Whitbread 87p weaker at 2364p and ITV 1.9p lower at 62.6p.