How Buncefield fire unfolded
The Buncefield fuel depot fire in December 2005 was the UK's biggest peacetime blaze. Below are key graphics, maps and satellite images showing what caused the explosion, how the blaze was tackled and its impact.
The Hertfordshire Oil Storage Terminal, or HOSL as it is also known, handled around 2.37 million metric tonnes of oil products a year - mainly petrol, diesel and aviation fuel - delivered by tankers and pipeline.
The depot, opened in 1968, is outside the town of Hemel Hempstead, 40km (25 miles) northwest of London and just off the busy M1 motorway, which was closed twice because of the fire. Some residents had to be evacuated from nearby housing, while offices and warehouses around the site suffered major damage.
Disaster struck early in the morning of Sunday 11 December as unleaded motor fuel was being pumped into storage tank 912, in the north west corner of the site. Safeguards on the tank failed and none of the staff on duty realised its capacity had been reached. By 0520 GMT, investigators believe, the tank was overflowing:
Under normal circumstances, gauges monitor the level of the fuel in the tank as it fills from a pipeline.
An automatic high level safety switch should trigger an alarm if the tank reaches its maximum capacity. This should result in shutdown.
But on this occasion, automatic shutdown did not happen and when fuel continued to be pumped in, it overflowed through roof vents.