Police are searching for a three-year-old boy who has gone missing with his mother.
Olly Sheridan is at the centre of a family court dispute between his estranged parents Ellie Yarrow-Sanders, 26, and Patrick Sheridan, 45.
A High Court judge earlier this week raised the alarm.
He said he is gravely concerned.
The court hearings have been staged in private and journalists had been barred from identifying the family, who come from the Basildon area of Essex, involved.
But Mr Justice Williams said he was lifting the identity bar in the hope that publicity would help find Olly and Miss Yarrow-Sanders.
He said they could be named and photographs of them published.
Essex Police said they are searching for the pair and a spokesman urged anyone with information to come forward.
A spokeswoman for the firm said the “live police investigation” is 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 has 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.