The mum of two boys attacked by Letby said she trusted her ‘completely’ (Picture: Cavendish Press/Getty)

‘Trust me, I’m a nurse.’

The new mum had only popped back downstairs to the neo-natal unit to drop in some breast milk for one of her seven-day-old twin sons’ 9pm feed.

They seemed to be doing well, and her husband left earlier that evening to get the house ready for her arrival once their boys had been transferred to another hospital closer to home.

But as she approached the intensive care nursery, the night-time quiet was broken by the sound of ‘horrendous’ crying ‘like nothing I had heard before’.

Inside, she could see one of her babies in deep distress, with blood coming from his mouth.

The nurse designated to look after them, Lucy Letby, sought to ease her worries, telling her it was probably just a feeding tube irritating his throat and that a doctor would be in soon to check on him.

Ushering her back to the labour ward, where she was still recovering from a Caesarean section, Letby told her: ‘Trust me, I’m a nurse.’

Asked eight years later why she did as she was told despite her concerns, the heartbroken mum replied: ‘Because she was an authority and she knew better than me and I trusted her. Completely.’

She sobbed as she told jurors at Manchester Crown Court: ‘I knew. I knew there was something wrong and I had known from leaving him but I left.’

But what she did not suspect – and never could have imagined – was that the person whose job it was to care for her son had been trying to kill him.

And she had unwittingly interrupted his murder.

Letby attacked the babies while working at the Countess of Chester Hospital (Picture: Chester Standard/SWNS)

The bleeding she noticed late on August 3, 2015, was actually caused by Letby shoving a piece of medical equipment down his throat.

Once she had persuaded his mum to leave them alone again, she tried a second time by injecting him with air. It worked.

Within a matter of hours, the infant suffered an inexplicable sudden collapse before dying in his parents’ arms.

It would become known as one of Letby’s preferred ways of killing babies.

That was the method she used just over a month earlier when she murdered three newborns and attacked another in the space of just two weeks.

Another was poisoning them with insulin, like she did to the other twin the very next day.

The corridor within the Countess of Chester Hospital’s neonatal unit (showing the entrances to nurseries 2,3&4) (Picture: PA)

The ordeal suffered by that family bears several of the horrific hallmarks of Letby’s year-long killing spree.

Targeting vulnerable infants shortly after their parents had left their cot-sides, or their nurses were elsewhere.

Inflicting repeated assaults to create the impression of a continuous problem where none existed.

And taking a ‘very unusual interest’ in the bereaved family afterwards.

Letby carried out social media searches on the parents two days after the twin’s death and again on several occasions thereafter, including on Christmas Day.

She claimed it was a habit fuelled by innocent curiosity, but prosecutors insisted she ‘revelled’ in what she had done and ‘enjoyed the anguish and distress’ she caused them.

Chillingly, the attacks were mirrored eight months later when she targeted another set of twin boys in almost identical circumstances.

The first was poisoned with insulin, with jurors at Letby’s trial told she doubled the dose on that occasion in a ‘cruel’ bid to ‘complete’ what she had planned with the earlier attempt.

She also tried to murder his brother by injecting him with air during the same shift.

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Letby also targeted two triplet brothers four months later, killing both. Each had liver injuries, while one also had his breathing tube dislodged.

Moreover, the bizarre behaviour after the killings wasn’t limited to August 2015.

Weeks earlier, she had to be told repeatedly to leave a room where grieving parents were spending their final precious moments with their dying son.

They were shocked when at one stage she wheeled a ventilator basket in, saying: ‘You’ve said your goodbyes, do you want me to put him in here?’

And two months later, in October 2015, Letby sent a sympathy card to the distraught parents of a baby girl she murdered on her fourth attempt.

A photo of it was found on her phone when she was arrested.

The sympathy card that was shown to the jury in the Lucy Letby murder trial (Picture: PA)

After she died, Letby and another nurse asked those parents if they wanted to bathe her a final time, with the former also offering to take photos as she had during her first bath.

The mum told jurors: ‘She was smiling and kept going on about how she was present at the first bath and how our daughter had loved it.

‘I wished she would just stop talking. Eventually she realised and stopped. It was not something we wanted to hear.’

Nick Johnson KC, prosecuting, said of the murder: ‘What happened to her followed the pattern of what happened to others before and what was yet to happen to others.

‘It was persistent, it was calculated and it was cold-blooded.’

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‘She was an authority and she knew better than me and I trusted her. Completely.’