The investigation to catch Lucy Letby lasted six years – which culminated on Friday with the 33-year-old nurse being found guilty of murder.

“We had to go right back to the start, keeping an open mind and being careful not to draw any conclusions,” said Det Supt Paul Hughes, the senior investigating officer who led the investigation

“The last thing we expected to find was a suspect responsible for these deaths and non-fatal collapses. It was a long, drawn-out process but no stone was left unturned. We had to do it right – not rush it.

“We had to deal with this as 17 separate investigations – we are normally used to dealing with one murder or attempted murder investigation at a time let alone something on this scale.

“What started out as a team of eight quickly increased and, at the height of the investigation, featured almost 70 officers and civilian staff working together.

“Turning up at the home of a family who have lost a baby, grieved for their loss and are trying to move on from that is difficult enough, but having to tell them that someone who was meant to be caring for their little one could ultimately be responsible for their death – is not an easy task.”