Sammy, my thoughts too. I'll keep this post updated with the results, though it might be a while.

Yes, please do update. Hopefully the stain isn’t permanent; what a shame that would be. Do you know if he’s been following the care instructions up till this point? I‘m surprised oil would make it past the wax barrier. Btw, what kind of oil is it—motor oil? cooking oil? Or perhaps it’s gun oil?

Don't know the top of oil, I would have to ask if he knows. What I do know, now that I've been to the Barbour web site is that the coats need re-oiling yearly and his would be with the Thornproof oil. It has a wet look when done. His coat looks very dry, so It hasn't been kept up by who ever had the coat in the past, or he could have got it new, but got it at a bargain; don't know. I'm thinking that the oiling will dilute the spot partially. The problem with washing or trying a solvent on the area such as Dawn, the base treatment would be removed and then it is not successfully oiled from then on.

video from their Barbour web site. The second video is a better video from another presenter and I will attach it as well:

Call Barbour. Don’t try anything on your own. My Dh sends his yearly. They will patch holes, so maybe they can fix the stain. Worth a call. Good luck!

Thanks for the info about repairs. I doubt if friend will be sending coat to England but I’ll run it by him.