A nanny "dangerously and excessively" shook a 10-month-old baby boy to death after she lost her tempter, a court has heard.
Joshua Paul was being looked after by child minder Viktoria Tautz, 34, who asked paramedics: "What am I going to tell his parents?"
Joshua was rushed to North Middlesex Hospital before being transferred to Great Ormond Street Hospital but died on 1 September in his parents' arms, the Old Bailey heard.
Tautz, who will be assisted during her trial by a Hungarian translator, denies manslaughter.
Prosecuting, Zoe Johnson QC said Joshua died "because of a head injury that caused bleeding in his brain, bleeding in his eyes and other brain and spinal injuries".
Opening the trial, Ms Johnson said: "On that day, for whatever reason... something snapped in the defendant and for a short while she lost her temper with Joshua and assaulted him, causing all those injuries.
"Her account of what happened whilst she was looking after Joshua does not explain Joshua's various injuries and therefore something else occurred - we suggest a dangerous and excessive shaking of Joshua - which the defendant has not revealed."
Joshua, who was born around 10 weeks early, was said to have a large head for his age, which was being monitored and a scan showed slightly dilated ventricles, Ms Johnson said.
Tautz, who the court heard "clearly loved" baby Joshua, began working for the family on after his mother returned to work.
Pearl Paul left her son in the one-bedroom flat with Tautz on 29 August at 8.40am and said Joshua was "happy and playing".
Tautz said in interviews that she had played a horse-riding game with Joshua but he had not had any accidents and she denied shaking him.
London Ambulance Service was called at 9.07am by a neighbour after Tautz emerged from the flat shouting for help and holding Joshua, who was unconscious and not breathing.
Paramedics arrived at 9.11am and found him lying on his back on the hallway floor while Tautz, who was "extremely distressed", was performing mouth-to-mouth resuscitation.
She told medics he had been crying in his cot, and that he "shook twice" when she picked him up, before he went floppy and stopped breathing.
Medical tests were later conducted at Great Ormond Street.
Doctors told Joshua's parents he had suffered "a devastating and irrecoverable brain injury from which he simply would not survive", his brain was not showing signs of activity, and his heart could stop at any time.
He suffered three cardiac arrests at Great Ormond Street and died at 10.55pm on 1 September.
In a statement read in court, Ms Paul said she paid Tautz £3.60 an hour, her son was "happy with her", and that she "never saw her lose her temper".
She said her son suffered from fluid on the soft spot of his head, had a large head, and that at an outpatient appointment on 22 July, 2014, doctors told her both of these had increased.
Joshua's parents were told to look out for three conditions related to the fluid on his brain.
Ms Paul said she was told that if he vomited, stopped eating or fell unconscious, he should be taken straight to hospital. She said this information had been passed to Tautz.
Describing the relationship Tautz had with her son, Ms Paul said if Joshua cried, she would hold him, adding: "She was good with him, so I was happy."
Joshua's father, Nirmal Vijayan, told the court that from the beginning doctors told them their son had fluid on his brain.
He said this was being "reviewed and monitored" and Joshua had not had any treatment.
Mr Vijayan said he never had to tell Tautz off for anything and she was a good nanny.
The trial continues.
Additional reporting by Press Association