So, I was cycling to the shops, and because I was checking out where I am going to start work tomorrow, I was coming along to town via the river path, where there is a nice cycle route.
I come to a bit in the path where the river bends to the left, and the path follows the bend, between the path and the river itself there is about 3m of a grass bank, which is about 1m above the height of the river.
As I come to this bend, I see up ahead a family also on their bikes, so I start speeding up so I can overtake them with the minimum of fuss, as I'm powering up to them, I hear a kerchunk, and the pedals lock up, forcing me off the saddle and almost on to the frame. I try pedaling again, but the chain is tight, and nothing happens, I veer to the right (towards the river) and on to the grass, noticing this I pull on my rear brake (If I pull the front brake I'm liable to go head over heals the speed I'm doing) and then turn to the left (away from the river).
This causes my rear wheel to slide, and the bike starts to skid, and eventually I end up facing the way I came with the rear wheel stopping about 20-30cm away from the edge of the river bank. I discovered that my chain had snapped off completely.
To make matters worse I was about as far away from my house that I could possibly get on the journey I was doing. The prospect of pushing the bike all the way home (and uphill) with my shopping was not one that I fancied, luckily there was a bike shop on the way home, so I took the bike there, and for about £75 (new chain, new front and rear cog sets + full service) I'll have a working bike by Saturday (they could do it before, but I can't make it whilst they are open due to the aforementioned job that I start tomorrow).
I still feel slightly shaken, and can replay it all in my head in slow motion (in all it can only have taken about 2 seconds from start to finish) if I close my eyes.