A consultant paediatrician whose testimony helped convict Lucy Letby has said he “should have had more courage” and voiced his concerns about the nurse sooner.

Ravi Jayaram told a public inquiry that he lay awake at night thinking about why he did not say something at the time.

“It’s the fear of not being believed,” he said. “It’s the fear of ridicule. It’s the fear of accusations of bullying.”

Letby was convicted of the attempted murder of Child K by dislodging her breathing tube before Jayaram walked into a nursery room in the Countess of Chester hospital’s neonatal unit in February 2016.

The prosecution at Letby’s trial said she was caught “virtually red-handed” by Jayaram, although he did not tell anyone at the hospital, or the police, about the incident at the time.

Giving evidence on Wednesday at the Thirlwall inquiry, Jayaram said he had been sitting outside the nursery reading medical notes when he realised Letby was alone with Child K and he felt “significant discomfort”, but also thought he was being “completely irrational and ridiculous”.

He decided to go in “just to make sure everything was fine”, he said.

“There has been a lot of speculation but I didn’t walk in and see anything. What I walked in and saw was a baby clearly deteriorating and when I went to assess Baby K the ET (endotracheal tube) was dislodged.

“My priority was to resuscitate Baby K, which I did successfully. I will take this with me to my grave. At that point I thought: how has that happened?”

Explaining why he said nothing about the incident at the time, Jayaram said: “It is something of a mea culpa. Why didn’t I? I lie awake thinking about this.”

He was worried about not being believed, or ridiculed, or being accused of bullying, he said. “I should have been braver and should have had more courage because it was not just an isolated thing. There was already a lot of other information.”

Jayaram said he first became aware that Letby could be causing “inadvertent or even deliberate harm” to infants when he returned from leave after the death of a baby girl, Child I, in October 2015.

He recalled conversations in corridors with fellow consultants about the repeated associated presence of Letby and sudden and unexplained deaths on the unit.

Jayaram said he did not believe that hospital executives initially took their concerns about Letby seriously.

He said he recalled the chief executive, Tony Chambers, saying to him: “I can see how that would be a convenient explanation for you, but surely there must be something else?”

Jayaram told the inquiry: “What I realise now is that, right from that point, there was a reluctance to consider what we were suggesting could be going on.

“I had no reason to not trust these people. You know they are wise and they are paid large amounts of money to run hospitals. I was too trusting … Well, why shouldn’t I be trusting the people who run an organisation in which I work? But it just didn’t smell right.”

Letby, 34, is serving a whole-life prison term after being convicted of murdering seven babies and attempting to murder another seven.

She has consistently denied harming any infants and is preparing a legal challenge to the Criminal Cases Review Commission. The court of appeal has rejected her attempts to overturn the convictions.