Sparky

I've seen exactly that behaviour due to a bad injector.  Check resistance values.

No code will be generated.

If I use anything, it'll be Wellseal.  Highly effective and not a disaster to remove next time.  Use of RTV should be punishable by death.

Spookily topical!  I did one yesterday that was just one tooth retarded and couldn't be adjusted to spec as the vacuum capsule was in contact with the oil filter.  Neither could I rotate the distributor enough to move the leads clockwise to compensate.  All I could do was remove the belt and retime the aux sprocket.  I'm sure the distributor/vac capsule were correct, so I'm a bit confused as to why this happened.
So, to qualify my referenced post:  if the sprocket is retarded and you have a vacuum capsule, you might have trouble adjusting the ignition timing!

Anyhow, having once more applied the skills that online gynaecological course taught me, I have deduced the thread is M14x1.5 - if I had the room, I'd put a feckin wheel nut on it.

Get a hacksaw blade down there and carefully cut through it opposite the split.  It'll soon shift!
Oh, and whereabouts in Herts?  I'm in Watford.

Correct!  And provided there are no other issues, no adjustment will be required on refit.  Just be careful of the paint when you lift, as they will pivot into the bonnet.

Roll pins come out only if absolutely necessary.  For engine/gearbox removal I always separate the spider and yoke.  Couple of minutes of very simple work.