Two black circles....one inside the other... Is this a possible place for diesel to leak?

Thanks everyone for your help. I think Biolandy might be right, it looks as if its coming from the large metal casing just behind the crank pulley, I first thought it was a gasket at the join of the block (lots of bolts around the edge holding it on.) Now though it looks like a small hole just...

Hi guys, forgive me if I've posted this in the wrong section but I figured it would be better than not posting it at all. Yesterday I took my 2.5l 96 discovery out; I don't use it very often (maybe once every two weeks.) I noticed a stream of diesel following me, after closer inspection...