A civil engineer whose three-year-old son has gone missing with his former partner says he is enduring a "living nightmare".
Patrick Sheridan, 45, who has not seen son Olly Sheridan or ex-partner Ellie Yarrow–Sanders for months, says he is "sick with worry".
Miss Yarrow–Sanders, 26, vanished with Olly in July while embroiled in family court litigation, centred on the little boy, with Mr Sheridan.
A High Court judge who has analysed the case at a hearing in the Family Division of the High Court in London on Wednesday issued an urgent appeal for information about Olly and his mother.
Mr Justice Williams said he was gravely concerned.
Family court hearings have been staged in private and journalists have been barred from identifying family members, 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.
Mr Justice Williams said his level of concern was such that he had decided to make Olly a ward of court – a move which places responsibility for a child directly in a judge's hands.
He urged Miss Yarrow-Sanders to return Olly and said evidence showed that children who were abducted by parents suffered long-term emotional consequences.
"We're trying everything to find Olly but it is clear that extensive steps have been taken to conceal where he is," said Mr Sheridan.
"He's been gone for months now and I miss him every single day.
"It's just been a living nightmare no parent should have to go through and I'm sick with worry".
He added: "The run up to Christmas has been unbearable."
Mr Sheridan went on: "My message to Ellie is simple: 'Please come back so that we can see Olly's alright'."
He said there was evidence to suggest that Olly and Miss Yarrow-Sanders might have been to Huddersfield, West Yorkshire.
Her family also had links to London and King's Lynn, Norfolk, he said.
Mr Sheridan is being represented by specialist lawyers from law firm Irwin Mitchell.
Barrister Andrew Bagchi QC, who is leading his legal team, had asked Mr Justice Williams to allow detail of the case to be made public in the hope of finding Olly and Miss Yarrow- Sanders.
An Irwin Mitchell spokesman said Miss Yarrow-Sanders and Olly had gone missing in July.
They had vanished shortly before Miss Yarrow-Sanders was due to give evidence at a "critical" family court hearing in Chelmsford, Essex, he said.
He said all attempts to find the pair had proved fruitless and Miss Yarrow- Sanders had defied judges' orders to return Olly.