The FTSE 100 failed to tap into strong momentum elsewhere as European and US equities rallied on positive progress on border security for the US-Mexico border, potentially avoiding another US government shutdown.
Germany's DAX jumped 1.1% to 11,136 and the Dow Jones rose 1.3% to 25,371 at around 4:45pm UK time.
At close, the FTSE 100 was only 4 points higher at 7,133.
Brent crude oil rose 1.7% to $62.58 per barrel.
MID AND LARGE CAP RISERS AND FALLERS
Online broker Plus500 tumbled 30.7%, despite almost doubling its annual profit. The company warned tighter UK regulations would cause it to post a profit in 2019 'materially lower' than market expectations.
Travel company TUI dropped another 7.4% as it posted a deeper earnings loss in its fiscal first quarter, while reiterating last week's shock guidance downgrade.
Pharmaceutical company Indivior shed 2.2% after a US court denied its appeal against a decision allowing rival Dr Reddy's Laboratories to sell a generic version of its opioid addiction treatment.
Train and bus company Stagecoach advanced 1.2% as it confirmed that subsidiary East Midlands Trains agreed a new short-term rail franchise with the UK's Department for Transport.
Insurer AA was broadly unmoved at 92p after announcing it expected its annual underlying earnings to be at least £340m, in line with its previous guidance range of £335m to £345m.
SMALL CAP RISERS AND FALLERS
Media consultancy Ebiquity warned 2019 profits for its consultancy business will be flat as cost pressures continued, causing the shares to fall 8.2% to 56p.
Data firm for the retail and transport sectors Touchstar rose 12.6% as it guided for a shallower loss than the market was currently expecting, due to margin improvement.
Logistics company Wincanton gained 1.3% on news that it had been selected by UK tax authorities to support air and sea freight inspections.