The main index, whose companies get more than two-thirds of their profit from abroad, was up 0.3pc at 0816 GMT, while the more domestically-focussed FTSE 250 was up 0.1pc.

The indexes outshone European and Asian counterparts, where confidence was hit by media reports the United States is considering Huawei-like sanctions on Chinese video surveillance firm Hikvision.

A slide in sterling led internationally-exposed companies British American Tobacco, Unilever and Diageo to be among the biggest risers on the FTSE-100.

In contrast, blue-chip housebuilders including Persimmon and Barratt lost more than 2pc after gaining in the previous session when May unveiled her new Brexit deal.

M&S slid 5pc to a more than four-month low after it priced a rights issue at a big discount to Tuesday's close.

It also reported a third straight decline in annual profit, emphasising the pain of its latest turnaround plan.

SSE slipped 2pc after reporting a slump in annual earnings and warning of an uncertain outlook due to the opposition Labour party's plans to renationalise energy networks.

Strong earnings reports lifted the mid-cap index, despite the pound's weakness.

Financial trading platform IG Group surged 9.1pc after it unveiled a plan to drive growth even as it forecast a drop in full-year net trading revenue and operating profit.

That helped rivals Plus500 and CMC Markets to gains of 4.4pc and 2.1pc respectively.

Royal Mail, the former postal monopoly, gained 7.2pc - its biggest one-day rise in 5-1/2 years - as investors focussed on the company's new five-year turnaround drive instead of a dividend cut.

Pets at Home jumped 10pc after reporting better-than-expected revenue and forecasting higher earnings for 2020.

Weighing on the index was engineering services group Babcock , which tumbled 9.1pc after saying it expected revenue and underlying operating profit to fall in 2019/2020.