A friend and work mentor of nurse Lucy Letby has told a public inquiry she cannot understand how she was “so blind” about the child serial killer.

The senior nurse, who cannot be named for legal reasons, said she is “learning with hindsight” about events at the Countess of Chester Hospital’s neonatal unit where Letby murdered seven babies and attempted to murder seven others between June 2015 and June 2016.

Giving evidence at the Thirlwall Inquiry into how Letby was able to carry out her crimes, the nurse, referred to as Nurse T, said: “It’s just so unbelievable. It’s just so out of my sphere of understanding.

“I find it so difficult to comprehend that anyone could do that – deliberately harm or kill somebody else, never mind a baby they are charged with caring for.

“I’ve always looked at my role as part of a multi-disciplinary team and our aim is to send those babies home with their families. We can’t do our jobs without trust.

“I still sometimes wake up going ‘How can it be true?’ I know it is, but there are things that have come out in this inquiry that have reaffirmed that for me. I can’t understand how I was so blind to it.”

Letby had told her and another nurse friend they were the only people she was talking to after she was removed from the unit in July 2016 and assigned to office duties, Nurse T said, but she now knows that was untrue.

Nurse T said she also knew “nothing” about her visits to Liverpool’s Alder Hey Children’s Hospital in 2017 arranged by a doctor who previously worked with Letby at the Countess of Chester.

She told the inquiry: “I’m learning now with hindsight. I didn’t see what was going on. I still find it really incomprehensible that we are in this position.”

Nurse T mentored Letby while she was a student nurse in 2010 and found her to be “very intelligent” and “capable” but said she could seem “quite aloof”, the inquiry heard.

She said she knew of the case of another child serial killer nurse, Beverley Allitt, and was “very aware” that changes were made to training and mentorship following her crimes in 1991.

Nurse T said: “I always took that seriously and if I felt I had concerns about a student I would have raised them.”

But she told the inquiry her “general impression” at the time was that Letby was a good student and a good future team member.

Nurse T said neonatal ward manager Eirian Powell had an “adversarial” relationship with consultants and that Ms Powell had dismissed their concerns about Letby as “nonsense”.

She said Ms Powell had a “dictatorial style” of management on the ward and had “clear favourites” including Letby.

Nurse T said: “She made comments that Lucy would go far, she had a great career, earmarked her as a good nurse.”

She said she thought Ms Powell was supportive of Letby after concerns had been raised by consultants and she had pointed out that, if you took out babies “born with congenital abnormalities”, then the number of deaths was in line with other neonatal units.

She said Ms Powell told her Letby was also “unfortunate” in that she did extra shifts and therefore happened to be there for more of the deaths, and that was the only thing the doctors had to “back up what they were saying”.

Nurse T added that Ms Powell said the doctors’ decision to carry out an external thematic review in late 2015 of the increased mortality was “all nonsense”.

Letby, 34, from Hereford, is serving 15 whole-life orders after she was convicted at Manchester Crown Court of murdering seven infants and attempting to murder seven others, with two attempts on one of her victims.

The inquiry is expected to sit at Liverpool Town Hall until early next year, with findings published by late autumn 2025.