Oil Leak #4 from the just acquired 2004 XK8 come from a line I can not identyfy. Line is part hose about 1/2" did and part metal tube that firs inside this hose. It passes directly by and above the top of the oil filter. It is no more than 2 inch from oil filter.

It looks like it has had a fix or a modification because this line is held to the wishbone by a plastic tie. I'll add a picture.

All and any enlightenment gratefully received.

 

Since you do not show endpoints, but the starter is showing
the best guess is a power steering line.

You can confirm locally by actually following the line to it's
two endpoints.

 

Yes I have come to agree with you. Almost impossible to get a hand on it to fix!