The FTSE 100 was up 1.1 percent at 1049 GMT, as the stronger dollar helped lift companies with international earnings. HSBC, which makes a big chunk of its revenue abroad, was the biggest contributor to the market's gains, followed by Shell, which was boosted by higher oil prices.
The more domestically focused midcap index was up 0.7 percent after Prime Minister Theresa May said she would fight a no confidence vote against her later in the day, as the saga over Britain's divorce from the European Union continues.
The pound was up 0.3 percent, suggesting traders reckon she will win the vote which could quash hard Brexiteers for good.
The Irish exchange Dublin, which has fallen 22 percent so far this year, was the only major European bourse in the red by midmorning. Ireland's economy is seen as highly sensitive to any negative Brexit outcome.
FTSE investors focused instead positive signs from the protracted US-China trade war, easing worries about the damage to global economic growth.
"The gains are reflecting lots of other news out there. Investors have attached to the trade story today," said Ben Gutteridge, head of fund research at Brewin Dolphin.
"It's hard to see a deal that would satisfy the Trump administration. The trade story is so loose, it's surprising it's such a powerful rally."
US President Donald Trump said he would intervene in the Justice Department's case against a top executive at China's Huawei Technologies if it would serve national security interests or help close a trade deal with China.
Mining stocks, BHP Group and Rio Tinto, were among the top gainers, in line with higher base metals prices, following Trump's comments, while the dollar held near a one-month peak against its peers.
Tobacco stocks British American Tobacco was up more than 2 percent after the world's No. 2 tobacco company stood by its full-year forecast. Peer Imperial Brands gained 2.5 percent.
Among the losers, Wood Group fell 6.2 percent to the bottom of the FTSE and its lowest since May as its cautious outlook on contracts as its oil-producing clients struggle with volatile prices outweighed an upbeat earnings outlook.
Housebuilders Persimmon, Taylor Wimpey, Berkeley Group and Barratt Development fell between 0.9 and 1.4 percent as investors shunned stocks seen as some of the most sensitive to a hard Brexit.
Retailer Next was down 1.9 percent to its lowest since January, as disappointing news from clothes retailer Superdry and phone and electronics chain Dixons Carphone further dented confidence in the battered retail sector.
Among the midcaps, Superdry plunged 32 percent and Dixons sank 8 percent to their weakest in more than five years, while Metro Bank lost 5.7 percent after a Citi downgrade.
Indivior fell 4.5 percent as buying ran out of steam after a positive US court ruling on its best-selling opioid addiction drug.