Fire & Brimstone at the Buncefield Oil Depot, Hemel Hempstead

0520 GMT: Calculations show that Tank 912 would be completely full and starting to overflow. Continued pumping causes fuel to cascade down the side of the tank and through the air, leading to the rapid formation of a rich fuel/air mixture that collects in bund A — the low enclosure surrounding 912 and neighbouring tanks.

0538 to 0546 GMT: CCTV footage shows vapour of escaped fuel start to flow out of the north-west corner of the enclosure, towards the west. The vapour cloud thickens from 1m deep to about 2m deep and soon flows out in all directions.

0550 to 0600 GMT: The pumping rate down the pipeline to Tank 912 gradually rises to around 890 cubic metres an hour, and the vapour cloud starts flowing off-site.

0601 GMT: The first explosion occurs, and further explosions follow, eventually engulfing more than 20 large storage tanks.