Total, the world’s fifth-largest oil company, today admitted health and safety breaches relating to Britain’s biggest explosion during peacetime.

The company’s UK arm was one of five defendants facing prosecution as a result of the huge fire at the Buncefield oil depot in Hertfordshire in December 2005. More than 40 people were injured in the blast, which caused millions of pounds worth of damage.

Total was accused by the Health and Safety Executive and the Environment Agency of failing to ensure the safety of its workers and others in the vicinity. It was also accused of allowing chemicals and fire to damage local water supplies.

At a hearing at the Old Bailey, Total entered guilty pleas to two charges under the Health and Safety Act and one under the Water Resources Act.

Total later issued a statement saying that it regretted the incident and apologised to those affected. However, it declined to comment further as proceedings continue against the other defendants.

Four other companies, including Hertfordshire Oil Storage, a joint venture between Total and Chevron, the US oil giant, that operated the Buncefield plant, pleaded not guilty to breaking health and safety laws.

The explosion occurred at 6am on December 11, 2005 and measured 2.4 on the Richter scale. It was so powerful that it could be heard as far away as the Netherlands.

The blast happened after staff failed to notice that a tank gauge had become stuck, causing oil to overflow. The tank filled past critical levels after a backup safety switch failed to trigger, causing the plant to fill with petrol vapour. Alerted by a tanker driver to the strong smell, the safety supervisor mistakenly shut off the wrong pipeline.

Total was sued for about £750 million by insurance companies, other oil companies and hundreds of local residents. Although Total claimed that Chevron should share liability for the incident, a High Court judge ruled in March that Total alone should bear the cost.

That judgment has been appealed and is due to come before the Court of Appeal early next year.

The criminal case against the other companies charged by authorities — Hertfordshire Oil, British Pipeline Agency, TAV Engineering and Motherwell Control Systems — is expected to begin in April.

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