I can hardly blame engineer Claude Baily who started developed on the Jaguar V12 as early as 1951. But somewhere along the line Jag added fuel injection, an a/c compressor and cruise control blocking any reasonable access to simply changing the spark plugs. It’s so bad around the compressor that plugs 1A and 1B often get left behind as some shops/people will cheat by only doing the other 10. It happened to mine. There were two old Bosch plugs running a gap of .040+” when they should be .025″. The other 10 Champion plugs were gapped at .035″ which is too big as well, but probably provided adequate spark without taxing the system too much.
Take a look at that last picture. See if you can spot the spark plugs. No? Either could I until I started removing all the fore mentioned stuff. I probably have four hours into tearing everything down just to change the plugs. Eeesh. I know it could go quicker. I blame myself for not knowing what the hell I’m doing with this V12.