Rain water is getting into the boot well of my car - what's causing this?

My 2017 Vauxhall Astra has a large quantity of water sitting in the well under the boot floor where all the battery and fuses are located. It has stopped all the dashboard from working completely, however the car still starts. It has been taken to the local Vauxhall dealer for investigation. It must have been happening for a while as there is visible rust in the boot. Have you heard of this before or know what might have caused it? Obviously it is under warranty but I am worried that unless it is rectified properly and the damage put right, it could re-occur and any visible damage could affect its future value on resale.

Asked on 13 March 2018 by JONATHAN COLLINS

Answered by Honest John
Failed one way cabin vent flaps. These are situated between the lower sides of the load area (usually hidden by carpet) and the rear bumper valence extensions. If they fail, water is splashed at force through them by the back wheels.
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