How do I remove a broken spark plug from the lead end of a W124 103 engine (1992 260E)? The plug is broken halfway through the ceramic. I can get the engine-side of the plug out but not the lead end. Is it possible to undo the metal boot? I notice it has a wire ring around it and several lugs.

Meanwhile I've ordered new leads and Beru plugs BUT I'd really like to whack a new plug in right now. It looks like its had this problem for awhile. The plugs Haven't been changed for 4 years and I notice there's a small hole (pitting) at the base of the plug hole near the head. Possibly from arking.

Amazingly, even though the spark-plug is broken in two the engine fires without a miss and the car drives fine.