I wrote a 2,500 word history essay (research, plan and write-up) in a day back in first year. Got 72% on it too! It was only a formative essay though, I'd have never risked leaving it so late if it actually counted towards my degree.
I found out on Monday that I have a 3,000 worder in for the 23rd, other work commitments mean I'll only have five days in total to research and write it which seems a scarily short time!