Mystery hole - fiesta sport van 1.5tdci

[outtadrally]

Hi all,

My fiesta sport van 2016 1.5tdci seems to be leaking from the rocker cover, however during investigations I noticed this hole. It looks like something should go in there? Should it be blanked off?
I had a cam changed before so just wondering did the mechanic forget to put something in? Oil does not appear to be coming from this hole even when running. The oil that can be seen comes from further up (I.e rocker cover)

[outtadrally]

[bungz]

Have a google.

All images seem to be blank that show that hole.