The FTSE 100 dropped in value on Tuesday as it was knocked by a slump in oil prices and a weak session for AstraZeneca.
Oil majors Shell and BP both dragged on the index after Brent crude oil prices sank to their lowest level since 2021.
The energy benchmark fell significantly after Opec opted to cut its forecast for oil demand in 2024 and 2025, while there was also pressure from concerns over tropical storms in the Gulf of Mexico.
A barrel of Brent crude oil was down by 3.9% to 68.58 US dollars (£52.49) as markets were closing in London.
Elsewhere, pharmaceutical firm AstraZeneca was among the weakest performers on the FTSE 100.
The drugs giant was a drag after it revealed that one of its lung cancer treatments missed targets in recent trials.
It said the trials for datopotamab deruxtecan, or Dato-DXd, failed to reach “statistical significance” for the overall survival of patients with a specific strand of lung cancer.
As a result, shares in the company fell by 2.4% to 12,406p.
London’s top index finished 64.86 points, or 0.78%, lower to end the day at 8,205.98.
Across the Channel, sentiment was cautious ahead of the European Central Bank (ECB) interest rate decision later this week.
The Cac 40 ended 0.24% lower for the day and the Dax index was down 0.89% at the close.
In the US, the Nasdaq moved higher as tech firms had a strong opening despite Apple dipping in value after Huawei unveiled a rival phone hours after the launch of the iPhone 16.
Axel Rudolph, senior technical analyst at IG, said: “Indices, yields and currencies were little changed as investors await this week’s US inflation print and ECB rate decision.
“The central bank is widely expected to cut its main refinancing rate by 25 basis points to 4.00%.
“US yields and the US dollar traded slightly higher ahead of widely awaited US inflation data.”
Meanwhile, sterling declined to another new three-week low after ONS data showed that UK regular wage growth slowed to 5.1% year on year over the three months to July.
The pound was down 0.07% at 1.306 US dollars, and was up 0.07% at 1.185 euros.
In company news, Wickes shares strengthened after the home improvements retailer said trading had improved so far in the latest quarter, with design and installation sales “stabilising”.
It helped support sentiment around the business despite it reporting a 24.8% slump in pre-tax profits to £23.4 million in the six months to June 29.
Wickes shares closed up 3.3% at 170.6p.
Shopping centre owner Capital & Regional was firmly in the red after a company which had been touted as a potential buyer said it was no longer interested.
Praxis Group, also a property firm, said it has “no intention to make an offer” for the group, which runs shopping centres in Edinburgh, Hemel Hempstead, Ilford, Maidstone, Walthamstow and Wood Green. Shares were 7.4% lower at 63.9p.
The biggest risers on the FTSE 100 were Unite Group, up 37.5p to 988.5p, JD Sports, up 4.65p to 140.5p, LondonMetric Property, up 4.8p to 207p, Howden Joinery, up 21.5p to 956p, and Fresnillo, up 9.5p to 514p.
The biggest fallers on the FTSE 100 were Barclays, down 7.3p to 216.7p, Melrose Industries, down 13.6p to 458.5p, Centrica, down 3p to 119.5p, AstraZeneca, down 306p to 12,406p, and Natwest Group, down 8p to 325.8p.