[tonupkid]

Adrian. Glad you got it started and everything is OK with yours.

This thread raises some issues, and as we A8 drivers would like to display our Samaritan qualities, when called upon, it would be good if we could get to the bottom of the risks involved in providing that vital spark to a fellow motorist.

As far as I can understand the risk in jumping to a dead battery is to the leads, they melt. So it makes sense to connect and run the donor for a while to get some juice into the recipient before turning it over.
If you could connect the running car to the dead one with massive leads, then surely the draw from a piddly Rover turning over would be loads less than the A8's own startup.

There must be some other reason why jump starting can mess up the ECU etc. Anyone know why this might be?

Incidentally I believe the connection sequence is. Get donor car running. Connect the + on each car first, then connect the - to an earthed (not - pole on the battery) part of the donor car, followed by the other end to an earthed (not - pole on battery) part of the donor.
Keeping the earth connection away from the battery reduces the risk of igniting the hydrogen/oxygen given out by a charging battery.