suspected
Yeah, I know. I do need to make sure that the oil hasn't just been there since before the rocker box gasket was changed.
When my car was last serviced I asked the guy whether he'd be able to change the rocker cover gasket (and I gave him a gasket). When he serviced it he cleaned it all, and tried to find where the leak was from. At the end he said he wasn't sure where it was comming from, but he suspected that it was the head gasket. He also said that it's such a small leak it's not worth worrying about. If it was the head I would've thought that it would've been pretty important to replace. It was however the rocker cover gasket, which has now been replaced (and isn't leaking).