After rising as much as 0.9%, the FTSE 100 ended 0.1% lower as base metal miners declined, tracking weakness in copper prices.
Limiting losses were oil majors BP and Royal Dutch Shell up 1.3% and 0.8% respectively as crude prices jumped after the producer group OPEC+ said it could review its policy to hike output at short notice if oil demand collapsed.
Insurer Prudential climbed 0.6% and Legal & General Group rose 0.6% after German peer Allianz raised its targets for shareholder returns for 2022-24.
Miners slipped 2.6%, but marked weekly gains of more than 1% as commodity prices bounced back from sharp losses seen last week after the new virus strain was detected.
"The worst case outcome looks a long way from priced in, and if the fears about the variant are realised, risky assets could still fall a lot further over the next few weeks," said Thomas Mathews, markets economist at Capital Economics.
"But if it proves to be benign, all the uncertainty over the past week will unwind very quickly and we will be back to the 'Goldilocks' environment of the preceding few weeks."
The FTSE 100 posted a 1% weekly gain, recovering some of last week's losses aided by a 6% weekly jump in energy stocks.
The domestically focused mid-cap index fell 0.3%, dragged down by weakness in communication services and healthcare stocks.
Home improvement retailer Wickes Group jumped 10.7% after it raised full-year profit outlook, saying it had continued to trade well in the fourth quarter so far.
Fund supermarket Hargreaves Lansdown rose 0.2% after appointing Amy Stirling as chief financial officer to replace Philip Johnson.
(Reporting by Bansari Mayur Kamdar and Amal S in Bengaluru; editing by Uttaresh.V; editing by Mark Heinrich)
By Bansari Mayur Kamdar