My job (ex job) is particularly dull, we drive small trucks, to deliver roll cages to dull premises, nothing much exciting ever happens.
To set the scene, we have a 3 vehicle wide loading bay just off the road, you can fit three 7.5 tonners in there just about (so close together you can barely climb out the doors). The bay is slightly sloped down towards the road, because of complications with pipework underneath the building.
The bay faces perpendicular to the direction of the road, so the trucks are all facing the opposite pavement, where there is an entrance to an office complex. All along the road there is ticketed bay parking, apart from the gap where our loading bay sits, and the gap on the opposite side of the road, that allows our trucks to pull out and turn. Courier vans/motorbikes pull up opposite our bay all day long to deliver to the offices.
Because of the weather, office workers were sat all over the street, on the curb, leaning on various walls etc enjoying the sunshine.
Stood on the bay yesterday, chatting to a few of the other drivers, same place I had been for about 45 minutes as the day was slow, and the heat was putting anyone off trying to find anything much to do.
All of a sudden, I notice the back of one of the trucks disappear from view, sliding off down the bay towards the street it went, deadly silence. Almost slow motion, I was barely able to utter “who is driving tha…” before it dawns on me.
I legged it out into the street after it shouting like a mad man in the hope of waking up anyone dozy enough to be sat on the curb, or perhaps stood in the wrong place facing the wrong direction. There would be no warning, for anyone, there was no noise.
The truck had been sitting there quite happily for over an hour, I had already been in the back of it that day, with the driver to help him unload the mornings work. 
It was one of those life flashing before your eyes moments, powerless to do anything. Having gathered a fair bit of speed from the slope (enough to bump start our trucks on several occasions) narrowly missing an 08 reg BMW parked in the last bay along, it charged up the opposite curb and across the pavement, luckily this took a hell of a lot of the momentum but not quite enough to stop is crashing into the building opposite about 3 feet from the entrance door and bouncing back onto the road.
By this point I was level with the drivers door, and went to dive inside for the handbrake, but the door was locked. Had no option but to let it roll back forwards again on the camber of the road, where the curb managed to stop it this time.
The office workers faces were a picture of dis-belief… for all of maybe 15 seconds after which they all went back to their conversations cool as cucumbers, as if nothing had happened! 
Thankfully nobody was hurt, but it could have been a bloody disaster if someone was sat in the way, or a courier bike/van was parked opposite as they are so often in the day. The bumper now looks like a version of a mccoys ruffled crisp, lightly speckled with cement and brick dust, and the boss may have to offer to get some re-pointing done on the building across the way 
I can’t really come up with a possible reason for this happening as it wasn’t my truck… something to do with heat expansion/contraction in operating cables or perhaps ratchet failure on the lever. The lesson might perhaps be to leave trucks in gear or to develop a deep mistrust of cable handbrake fitment on budget light trucks.
Definately a defining memory of my penultimate day at the place. 
Thanks for reading.
It wouldn’t be my choice if they were. Got enough hoop jumping on our plates already as drivers, thanks to their idea of risk assesment. The vehicle is already undergoing inspection for the fault.