A mother who ran away with her seven-year-old son has been told he could die if he does not receive cancer treatment for his brain tumour.
Sally Roberts went into hiding with Neon on Wednesday sparking a nationwide search before both were found unharmed.
At the High Court, she said she was not a "bonkers mother", but feared radiotherapy could do long-term harm to her son.
The court is expected to rule on whether Neon should receive treatment.
Doctors have said it was "clearly" in Neon's best interests to undergo radiotherapy and chemotherapy.
A lawyer representing the health authorities who are treating him told the court the "alternative is death".
'Every parent's nightmare'
A barrister outlined Ms Roberts's position in written arguments at the start of the hearing in London.
"Much sympathy it is hoped will be felt for her overall position," said Robin Tolson QC.
"The mother's position in this litigation ... is principled, reasonable and in the best interests of Neon."
Ms Roberts apologised to the court and said she only wanted the best for her son.
The judge, Mr Justice Bodey, is being asked to decide whether it is in Neon's best interests to undergo treatment.
He said Neon's illness was the "stuff of every parent's nightmare".
Mr Justice Bodey added he might not have sufficient time to rule on Friday, in which case his judgment would be given on Saturday morning.