Some plug missing on a 200tdi cylinder head assembly

Guys, on my defender 200tdi rocker cover, other than the rocker cover gasket, there is on the front and the back a small semi circle hole, which is located below the rocker cover, seems to be the cylinder head assembly, is that the place for the Engine block core plug? My mechanic says that those two semi circle holes need to be plugged, as oil is leaking from there. (See page 184 on the parts manual and you can see on the front and back of the head assembly there is a semi circle hole, which has a groove, looks like that grove is for a plug of some sort.
Can't find it in the parts book at all. Will try and get a picture. If anyone knows then can you give me the part number please.

Here are some pictures:-


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Its the small semi circle hole. Is this to be plugged with a rubber plug or it has to be kept open. There is another one at the back too.


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ERR765 ( plug-cylinder block oil way )

Hope this helps

thanks a ton

thatas clean......