My 1992 Disco Tdi has never had its swivel pin housing bolts removed. So, they are a bit corroded... Having acquired all the metric and imperial sockets I thought I would need, I now see that these are 12 point bolts and not the usual 6 point! And as they are a bit corroded I want to make sure I get the right socket or spanner on them and not round them off because accessibility is not their strong point. The Haynes manual shows a standard 12 pont ring spanner being used held between finger and thumb but I would really like to use an impact socket driver to get these off but I think I can just about manage with a standard socket. Can anyone confirm that these are imperial bolts?

Any suggestions for getting these off without shearing them? I guess I need penetrating oil, something to hit the bolts hard (a brass or bronze rod although even getting that in position looks difficult), heat and lots of patience.

Carefully chip away any major rust, then get some oil in there, and give each one about 20 knocks with a small hammer... more oil... time... then they should start to ease off.

Success! As suggested, got rid of the rust, lots of oil, brass rod and hammer to shake the bolts and then some heat (blowlamp). The bolts are 14mm and the only way I got them to move was to place a hydraulic jack under the spanner and gently raise the jack, it worked . no sheared bolts or rounded bolt heads BUT I now have a bent spanner.