The alternator is normally attached in parallel to the battery.
Yup, the diodes give the battery DC (which it likes) instead of AC (hich kills it in short order). What I meant was (and explained badly) that each AC Delco/Lucas/Valeo alternator I have come across that includes both rectification and regulation, has some polarity reversal protection built into the alternator to stop the regulator blowing (unlikely as that is) when the voltage reverses. In theory, the diode(s) they choose is usually up to taking the inrush current for any inductive loads that might still take current in the event of a reversal. I have even blown one (expensively) in a rather stupid attempt to reverse my battery, to prove it

I also agree about the sparks - but by the time you see the spark, it's already too late as it implies a back EMF as the load disappears - but then, you can avoid the situation occurring by connecting the leads in a definite order, and when the jump has succeeded, taking them off in reverse. I have done this on literally hundreds of cars, most of them modern, and I have had zero failures.

Finally, I only ever do my own jump starting - that's why I carry a set of specially rigged & taped set of start cables in each car!

PS Have you sold that Mk1 yet?

One of the few remaining Mk1 owners... #00015