A judge said 7-year-old Neon Roberts should receive radiotherapy against his mothers wishes today.
Sally Roberts said she feared that radiotherapy would cause long-term harm to her son Neon, and argued that "credible" alternative treatment was available.
Specialists treating Neon accepted that there were side-effects to radiotherapy but said that without the treatment the youngster could die within a few months.
Mr Justice Bodey, who heard evidence at a hearing in the Family Division of the High Court in London, said radiotherapy treatment could start.
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Jeremy Corbyn's visit has been one of the big talking points of another busy day at Glastonbury.
The Labour leader said socialist politics would not be put "back in a box" as he appeared on stage at the festival.
Turning windier with a few showers