By Sarah Mukherjee
BBC environment correspondent
It was 6am and Blue Watch fire crew, based at Hemel Hempstead fire station, were coming to the end of an unremarkable, if chilly, shift.
But instead of going home to a well-earned rest, they found themselves dealing with the biggest peacetime explosion in western Europe, the scale of which was such that for the first hours it was simply too big a fire to fight.
When the switchboard lit up, the fire crews leapt into action.
Twelve men and two fire engines answered the first call and initially, there was no reason to expect they were going to anything out of the ordinary.
Until they got closer.
Watch Commander, John Bachelor, said: "It was like something my father described to me during the Blitz, when you could see the whole of London lit up.
"It was on that sort of scale.
"All our training had been around one tank fire. This was just the lot."
As Mr Bachelor points out, this was an accident which should never have happened.
That was considered so unlikely it was not dealt with in any of their emergency planning.
It was assumed there would be one explosion in one tank but in the end, a series of events led to more than 20 going up, including the pumphouse which was to be the firefighters' first line of defence.
Brendan Langham said: "I've done seven years in the service, and there are guys who've done 25 years. They were just as horrified."
The firemen were told six people were unaccounted for.
Their first action was to try to find them before any more explosions happened.
Fireman Langham added: "You imagine what they guys in 9/11 must have felt.
"We were just running through this inferno, calling out for people."
Major incident plan
The six missing people were quickly accounted for and a major incident plan was put into place.
The fire was eventually put out within a couple of days, but fire crews were on the site until the New Year, coming from as far afield as Cornwall and Scotland.
According to fire chiefs, the public recognition of the work they did was overwhelming from the mince pies and Christmas cake which was brought in over the festive period to the lasting bond formed with the local community.
Hemel Hempstead fire station still has the books of letters from children thanking them for what they did during Buncefield.
Station manager, John Smith, said: "They make it all worthwhile."
Buncefield: One Year On will be broadcast on Thursday 7 December on Radio 4 at 2000 GMT.
You can also listen online for 7 days after that at Radio 4's Listen again page.