Disco 2 Oil leak from top/back side of engine

Hi All
I have found oil on the FPR, starter motor and also on the right back part of engine block which seems to come from somewhere from the top back side of the engine.
It is hard to see only felt by my hand.
I have found a round rubber part fixed by screw which was quite oily. What could it be? See photos.

That is the rubber washer thingy that holds the rear engine cover in place.

Cheers

So probably it comes from the rocker cover gasket.

berg450 said:

So probably it comes from the rocker cover gasket.

Click to expand...

Very likely. Mine leaked over everything and made a mess. New gasket fitted in January, a week later, the head gasket went... so obviously it was done again, no more oil leak.
However... I've noticed it's weeping slightly again...

Any opinion about the quality of gasket? Genuine only or OEMs are also reliable?
I changed mine a year ago, do not remember the make but not the cheapest, and it leaks, not much but it can be seen on the bottom of the engine.
The problem could also be in my case that the previous owner has used instant gasket (plus the original) which was very difficult to remove from the sealing surfaces. I would need to check the surfaces also for damage or remaining material....