Pull the e brake it’s literally in the handbook we’ll it was in my ZS as I recall for emergency use and yes I tested it (safely) it’s an electric old school style brake not related to EV so it’s going to help regardless.
Some of those I pace have the bad battery chemistry too from what I recall in recent news something else Jaguar has refused to put right
Let’s be clear though it’s not an EV matter this can happen to any new vehicle happened to Toyota in the US I think it was and others in fact the recent 3 cylinder eco boost recall the wet timing belt breaking up destroyed oil pressure causing loss of vacuum boosted braking and caused several crashes not to mention many dead engines that ford UK has refused to acknowledge despite the US recall.
Anyway point is this scenario is terrible and frightening but we are responsible for the cars we drive so we must have a plan in case the worst happens this was why I fully read the manual and then tested emergency procedures so I knew.
Hope everyone involved is ok and the defects get rectified to prevent any further incidents