1.8T BAM engine oil leak

[RedCupraR225]

Hello, long time lurker, first time poster. I'm hoping someone here can offer some advice. The car is a Mk1 SEAT Leon Cupra R, 1.8T BAM engine. Looking at the attached image, you can see what looks like a ball bearing in a hole on the right-hand side of the cylinder head. I'm confident that oil is weeping from this hole, as is the local German car specialist that looks after the car, although they've said that they've never seen oil leaking from here before.

Can anyone tell me exactly what I'm looking at? Is is related to an oil rail/gallery? Any advice gratefully received.

Tim

Edited by RedCupraR225 on Saturday 18th December 15:24