Don't suppose you could get a drill in behind that dowel and persuade it out?
That was plan A. Unfortunatley the dowel is hollow, and a bolt goes up the middle of it into a threaded hole. The bolt is M12, and the I/D of the dowel is about 14mm. What that means is the other end of the hole that the dowel fits into is a smaller diameter than the dowel, so you can't just drive/punch it out from the other side.
Plan B was to tap a thread into the inside of the dowel, then insert a bolt with that thread, and pull it out. But I don't have an M16 end tap, my M16 1st tap won't go in far enough to cut a thread, and even if it did I don't think I've got any M16 bolts.
I've tried mole grips , but not surprisingly they didn't work. I've got some M16 and M18 drills, but couldn't find my hand drill - must be here at home somewhere. And working under the car is a bit iffey with an 80+Kg box on a trolley jack, so I think the wretched thing is is going to have to come out again.