If you're charging your car while it's parked in the street, there's the possibility that a member of the public might trip over your car's charging cable.
This opens you up to allegations of negligence and a personal injury claim.
Under Section 4 of your Admiral motor insurance policy ('Liability to other people'), so long as you've taken reasonable steps to prevent such an accident or injury from occurring, you're insured against this.
The cables would be covered if they were bought as part of the car. Aftermarket cables aren't covered unless they were a direct replacement from the manufacturer.