Tough one to callNot sure about that James, if you found a C1 and did not inform the tenant, by way of an electrical danger notification, or temporary repair and informing the tenant, and then someone was hurt, I think you may well find yourself in court.
You didn’t create the problem, only found it.
Your legal duty is to inform the customer promply
What law would you be breaking?
Like I said, we all make our own morel decisions