Police are searching for a three-year-old who vanished with his mother during a family court battle.
Olly Sheridan disappeared from Basildon, Essex, with parent Ellie Yarrow-Sanders, 26, in July.
The boy is at the centre of a family court dispute between Ms Yarrow-Sanders and his father. Patrick Sheridan, 45.
The court hearings had been held in private and journalists had been barred from identifying the family, but a High Court judge has lifted the reported restrictions to allow for the police appeal.
Mr Justice Williams, who has overseen a hearing in the case in the Family Division of the High Court, said he was gravely concerned.
He said they could be named and photographs of them published.
Essex Police said they were searching for the pair and a spokesman urged anyone with information to come forward.
Mr Sheridan's law firm Irwin Mitchell said the live police investigation was a “big step forward”.
Mr Sheridan said: “I'm so grateful the police are helping to find Olly. Every day has been a battle but I know everyone is doing their best to help find my boy.”
Mr Sheridan urged people to rack their brains and think if they have seen Olly.
He said Olly might have been taken to see Santa and wants members of the public to think if they have seen the youngster in a grotto.
Additional reporting by Press Association
