A senior doctor has told a public inquiry he thought someone could be harming babies after he was told nurse Lucy Letby was on duty for three baby deaths in June 2015.

The child serial killer went on to murder four more infants on the neonatal unit at the Countess of Chester Hospital before she was moved to clerical duties in July 2016 after consultants raised concerns about Letby with executives.

Giving evidence at the Thirlwall Inquiry on Tuesday (November 19) into the events surrounding Letby’s crimes, neonatal clinical lead consultant Dr Stephen Brearey said the June 2015 deaths were “unusual” as they amounted to the normal annual mortality rate.

When he was told in a meeting by the unit’s nursing ward manager on July 2 that Letby was identified as the one member of staff present on each occasion, he said his first reaction was to say: “Oh no, not Lucy. Not nice Lucy.”

Dr Brearey told the inquiry: “It was a spontaneous comment when her name came out. It didn’t necessarily signify anything.

“The whole of the nursing team that we worked with I believed to be good people so I probably would have said that for any of the nursing staff to be honest.”

He said at the time when he conducted a review of those deaths he did not believe Letby’s presence was “overly concerning” because it was a small unit and nurses could condense their shifts, and that clusters of deaths would not necessarily be spread out across a year.

Counsel to the inquiry Rachel Langdale KC asked: “Why ‘oh no, not nice Lucy’? What was the point of the ‘oh no’, what was the link being made in your mind?”

Dr Brearey said: “Well obviously some part of my mind was thinking the worst.”

Ms Langdale said: “What did your mind jump to?”

Dr Brearey said: “The concern that there might be someone harming babies.”

Asked if he was aware at the time of Letby’s attack spree about fellow child killer nurse Beverley Allitt, the doctor said: “I remember discussing it with colleagues because I think we were all aware of the case historically.

“It was there and might have been the reason why I said ‘not nice Lucy’. But there is one thing to be aware of it historically and another thing to be considering it might be happening on your unit.”

Dr Brearey said the death of a baby girl, Child I, in October 2014 was a “significant moment that raised my level of concern quite considerably”.

The medic said the youngster’s death after a series of collapses following her return to the Countess after periods of stabilisation when she was transferred to another hospital had “set a few alarm bells going”.

Ms Langdale said: “By the time of Child I you thought that deliberate harm may be being caused here?”

Dr Brearey said: “Yes, there was considerable concern at that stage.”

Ms Langdale said: “And even before then at the meeting in July when you said ‘oh no’, a causal link was made that someone could be doing this in bad faith?”

“Yes,” said Dr Brearey.

Ms Langdale said: “How is it if you thought someone could be killing babies in bad faith, or harming them, you didn’t make a link with deteriorations, or what we now know are attempted murders, to think what are the cause for them?”

Dr Brearey said: “I accept it wasn’t in my mind and it’s obviously something I have reflected upon and it should have been.

“It probably comes down to the workload I had at the time in doing this. Most of the reviews were done out of hours.

“Dealing with mortality on their own was quite a considerable workload along with my other duties. On reflection I do feel there was a lot of clues and incidents, in terms of the morbidity side of things, that would have brought us to the conclusion earlier that something was wrong.”

Dr Brearey added he thought the reporting culture on the unit was good and that staff were very aware to report things that they thought went wrong, but “in retrospect” believed some of the incidents occurring between June 2015 and June 2016, and “probably before”, were deteriorations of babies that could have trigged further investigations.

He said: “On reflection I think it’s likely that Letby didn’t start becoming a killer in June 2015, or didn’t start harming babies in June 2015. I think it’s likely that her actions prior to then over a period of time changed what we perceived to be abnormal.”

Dr Brearey said he was “exceedingly worried” following the death of Child O in June 2016 as he noted an “unusual” rash which he thought may have been similar to previous rashes seen in 2015.

At the start of his evidence Dr Brearey apologised to parents of babies who Letby attacked and parents who are “involved in the ongoing police investigation”.

He said: “I’m sorry for my part in not being able to protect your babies. I can just say that I tried my best, and I acknowledge that at times my best was not enough.

“I hope you all get the truth and justice that you deserve.”

Dr Brearey acknowledged that the omission to note and appreciate blood test results in August 2015 and April 2016 which showed abnormally high insulin levels in two baby boys – who Letby poisoned – was a “collective failure” of the consultants, together with laboratories in Chester and Liverpool and “the system generally”.

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, between June 2015 and June 2016.

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