How do you open the bonnet of a3 when the cable has broken?

If the bonnet release cable has broken, you can try to access the latch directly by reaching through the grille or under the front of the car. Use a flashlight to locate the latch mechanism and a long tool, like a flathead screwdriver, to push or pull the latch to open the bonnet. Alternatively, if you have access to the cabin, you might be able to remove the under-dash cover to access the cable mechanism. If these methods fail, consider seeking professional help to avoid damage.