An inquiry into the murders committed by former neonatal nurse Lucy Letby has found that Dr Mark Deakin, a hospital registrar who exchanged over 1,300 messages with her and was described as her "boyfriend," repeatedly prioritised protecting her over his professional duties to patients. Inquiry chairman Lady Justice Thirlwall concluded that Deakin "blurred boundaries" by warning Letby about colleagues' suspicions and sharing confidential details from meetings held to discuss deaths and illnesses on the neonatal unit, actions she called "most unwise."

Deakin, who died earlier this year after being sacked over the messages, forwarded Letby confidential information following a 2016 staff meeting about babies who had died or fallen ill under her care, telling her to "keep this to yourself." He also failed to recognise the significance of dangerously high insulin levels in one of Letby's victims while on duty, an error Thirlwall attributed directly to him rather than a "collective failure." The inquiry further found his support for Letby continued into 2017, when he helped her secure a placement at Alder Hey Children's Hospital without disclosing that she had been barred from neonatal care at the Countess of Chester Hospital.