A father-of-four has lost the latest round of a "worrying" family court battle over the care of his youngest child.
Social workers at Brighton & Hove City Council had raised welfare concerns shortly after the little girl, now four, was born.
Judges have been told that the children's mother had mental health problems and was unable to safely care for them.
A local family court judge had decided in the autumn of 2013 that the three eldest children - now aged 13, 10 and eight - should live with their father.
But that judge said the little girl should be adopted - and social services staff had placed her with a couple who wanted to adopt.
A High Court judge then ruled that the little girl should return home, after her father appealed. Ms Justice Russell complained that social workers had been ''unprofessional'' and had talked ''psycho-babble''.
The couple who want to adopt then challenged Ms Justice Russell's decision - and the little girl stayed with them pending the outcome of their challenge.
Now the most senior family court judge in England and Wales has ruled that the little girl should stay at her adoptive home.
Sir James Munby, President of the Family Division of the High Court, said the "sad reality" was that the little girl had no "meaningful relationship" with her birth family and saw the couple she lived with as "daddy and mummy".
He said the case was "worrying" but concluded that moving the little girl back to her father now would probably cause her distress and trauma.
The judge said the couple could formally adopt.
"This is a very complex and worrying case," he said in a ruling published on Wednesday.
"It is, I think, by some margin the most difficult and concerning case of its type I have ever been involved in."
He added: "I am, at the end of the day, driven to the conclusion, which in the event I arrive at unhesitatingly, that (she) must for her own good and her own happiness... remain with what for her is her family."
Copyright (c) Press Association Ltd. 2017, All Rights Reserved.