A man has been arrested over a missing laptop used by Poppi Worthington's father to watch pornography on the night the 13-month-old was sexually abused and died.
Paul Worthington, 50, told police he viewed "adult X-rated" porn on the laptop but officers did not seize the computer and it has never been recovered.
It was one of a series of failures by Cumbria Police who lost vital evidence during their botched investigation which meant no-one has been prosecuted over Poppi's sexual abuse and death.
Cumbria Police made no "pro-active" attempts to trace the laptop, which Mr Worthington said he had sold to another man.
But after criticism of the investigation, the force made an arrest, last week, more than five years after Poppi's death.
A spokesperson said:
Mr Worthington will not face any legal action the Crown Prosecution Service ruled last week despite a court three times having found he probably sexually abused his daughter before her sudden death.
He denies any wrongdoing and is now living in hiding with the help of police protection.