The FTSE 100 was down 0.2% by midday as US and Chinese trade negotiators prepare to meet ahead of the potential introduction of new tariffs on Friday and as several shares traded ex-dividend.
Equities in continental Europe were weaker still, with Germany's DAX index down 0.7% and with US futures pointing to material declines on Wall Street later.
LARGE AND MID CAP RISERS AND FALLERS
Telecoms firm BT shed 1.7% even as it maintained its dividend after reporting annual results in line with expectations as growth in its consumer business was offset by regulatory pressures and declines in its enterprise businesses.
Supermarket Morrisons slipped 0.5% after it reported a 2.3% increase in Group like-for-like sales excluding fuel in the first quarter amid continued 'robust' retail sales performance despite ongoing political and economic uncertainty.
Housebuilder Barratt Developments added 2.2% as it said its outlook for the year was modestly ahead of its previous expectations amid a strong start to the year driven by good customer demand.
Defence firm BAE Systems edged 0.4% higher as it maintained its guidance after reporting that its start to the year had been in line with expectations amid ongoing improvements on several fronts.
Fashion brand Superdry rose 0.9% even as it said that trading continued to be weak and expected its underlying profits for the full year to be below analyst forecasts.
Insurer RSA advanced 1.8% as it said its first-quarter results were in line with its demanding plans for the period, adding that its underwriting actions were also on track for improvement after a challenging 2018.
Beazley lost 2% after it said premiums grew double-digits in the first quarter of the year, but that higher-than-normal levels of claims in its marine, property and reinsurance businesses continued to keep a lid on growth.
National Express gained 0.6% as it said it was on track to meet its full-year profit and cash flow expectations after strong Easter trading and a positive start to 2019, which saw it deliver growth in every division.
Energy services group Wood declined 1.4% after announcing it had appointed industry expert Roy Franklin as its next chairman, effective from 1 September 2019.
Packaging and paper group Mondi lost 0.3% even as it posted a 16% increase in first-quarter earnings, driven by a combination of higher selling prices, strong operational performance and lower-than-expected planned maintenance shut costs, as well as contributions from completed capital expenditure projects in 2018.
Derwent added 0.4% after it said strong occupier demand in the first quarter bolstered lettings growth quarter on quarter.
SMALL CAP RISERS AND FALLLERS
Retailer Findel gained 5.1% as it guided for results covering the 12 months to 29 March to come in slightly ahead of expectations.
Smart radio specialist Frontier Smart Technologies dived 41.7% as it reported weakening profitability in the face of rising competition.