Axel's mother, Linda Peanberg King, told St Pancras Coroner's Court that she and her husband Alistair made contact with the Harmoni centre in the Whittington Hospital in Archway, after their son fell ill on the night of October 30 last year.
Five days later - after consulting at least three doctors - he died from bronchopneumonia.
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Declan Donnelly will host the show alone when the show returns on March 31 following his partner Ant McPartlin's return to rehab, ITV says.
The campaigners have raised concerns about former undercover officers being granted anonymity during the proceedings.
The Discovery School in Newcastle has said there was "no excuse" for the serious error.