I had the same problem with mine. Even with a 6 point spanner, it was rock solid. I had tried holding the spanner on to the plug whilst persuading it with a hammer. One of the hits sounded quite a bit duller than the others. I'm sure that the scar will fade a bit with time. I ended up getting the spanner as horizontal as possible but still with some travel left..... right kids, don't try this at home (risk of severe injury / death). I eased my bottle jack up to the opposite end of the spanner. One pump, wait. Check everything is still ok (spanner fully on the plug, jack securely under the end of the spanner, if any doubt, lowered, re-positioned and started again). One pump, wait. The landy was rising and then it gently lowered. I still couldn't move the plug and so used the jack again, job done. I'm just telling you what I did. You're all grown ups..... most of you are grown ups..... ok some of you may be slightly grown up. Just bear in mind if that spanner flies off it will be travelling at speed and it has some weight to it. At best it will hurt. At worst it won't.