Bark full of tumours.

Poor thing ;o(

I think the tree is healthy, it just has these strange bumps on the trunk.

Sometimes caused by disease or when the tree has been damaged.

You mean it is something like "overhealing"?

Yes, it's scar tissue if damaged or in the case of disease like bigger versions of galls that appear on branches especially oaks. I'm no expert, just putting together the basics from web searches.

OK, thank you. Will go to some links too.

LOL, Homebird. You are RIGHT. I did not realise it.