The FTSE 100 Index fell 0.33% to 6,004.70 points today, led by losses among oil heavyweights, Tate & Lyle and GlaxoSmithKline.
BP fell 1.48% to 664.50p, Shell dropped 0.42% to 1,886p and BG declined 0.41% to 725.50p after Goldman Sachs cut estimates across the sector and May crude drifted back 74 cents a barrel to $66 in US trade.
GlaxoSmithKline fell 1.51% to 1,500p after it was downgraded to "neutral" from "buy" at UBS following disappointing results for Advair.
Tate & Lyle also dropped 1.91% to 564.50p as a consumer advocates group in the US suggested its Splenda sweetener could cause digestion problems.
Meanwhile, Severn Trent gained 6.31% to 1,197p after it announced it is to demerge its Biffa waste-disposal business by the end of this year.
BAE Systems also gained 3.66% to 439.25p as reports emerged it had discarded its bid for defence firm L3 Communications.
Miners finished mixed, with Rio Tinto closing down 0.29% to 3,044p and BHP Billiton gaining 0.31% to 1,122p.
In the US, the Dow Jones Industrial Average has gained 48.18 points, or 0.4%, to 11,193.12 points as the price of oil drops, boosting enthusiasm profit growth will help equities build on their best first-quarter performance in seven years.
Merck has added 23 cents to $35.64 after the drugmaker said first-quarter profit excluding restructuring charges was as much as 75 cents a share, helped by sales of the high-cholesterol treatment Zocor. Analysts, on average, expected 64 cents, according to a survey by Thomson Financial.
3M has added $2.02, or 2.7%, to $77.86 after it said it is considering a sale of its pharmaceuticals unit to focus on products which take less time to bring to market.
Caterpillar shares have also gained $1.46 to $74.96. The company stands to gain as much as $5bn in sales as a boom in oil squeezed from Canadian sand boosts demand for mining trucks and parts.
Aflac, the world's largest seller of supplemental health insurance, added 85 cents to $45.50 after the stock was raised to "overweight" from "equal weight" at Morgan Stanley.IFAonline
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An added tier of asset management can of course deliver additional benefits for certain investors, writes Graham Bentley - just be sure you can justify it to the regulator and, especially, the client