Update the morning after:
It was the Tesco roundabout on the A127 in southend, next to the big RBS.
There was a line of diesel looking more like something had ****ed it out rather than dropped it from a smash.
It was rush hour so I didn't get a chance to take any pictures of it, despite trying. I went back at about 11am and couldn't really see much, I assume the amount of traffic going threw had spread it around much more.
I know that there are lorries coming down the A127 for southend/shoebury and obviously the tankers for the fuelling station in tesco + their stock. Plus, as you probably know John, is a notorious roundabout for being a bit greasy anyway.
On a happier note, I wont £100 playing poker last night and I'm going to see top gear live today.