The detective who headed the probe into the death of a 11-week-old baby boy described it as “one of the worst cases I’ve seen in more than 20 years”.

Det Insp Lucy Thomson said: “You really can’t get any worse than the death of a baby; it’s horrific that somebody can behave in that way.”

She was speaking to BBC Radio Cambridgeshire following the airing of a Channel 4 24 Hours in Police Custody documentary into the death of Teddie Mitchell.

Kane Mitchell, 32, subjected Teddie to a ‘violent assault’ at the flat where he lived with the child’s mother, Lucci Smith.

Mitchell was jailed last year for life. Smith was given a two-year community order for neglect.

DI Thomson spoke of her sadness surrounding the case.

“You could see by the injuries,” she said. “It wasn’t just a one-off moment of anger.

“This was a little boy who had been subjected to horrible abuse over his very short life."

DI Thomson was asked what it’s like to be on the receiving end of a phone call to a case similar to Teddie’s.

“It’s always awful when you hear that a child or baby is hurt or poorly but you don’t know at that stage what you’re actually dealing with,” she said.

“There could be all sorts of scenarios that play out in front of you but it’s always really important to keep an open mind.”

DI Thomson admitted her job is “brilliant”, but agreed it did come with real pressures and sadness.

“It's about learning how to accept those feelings and to go with them sometimes but to know that you’ve got to be completely professional,” she said.

“Little Teddie, he needed us to be on our A game and to be thinking really carefully and rationally about what had happened to him."

DI Thomson said she would never be able to make sense of Teddie’s case.

It, was she said, “horrendous”.

Baby Teddie died at his St Neots home with 17 broken ribs, fractures to his skull, a bleed on the brain and spinal and eye damage.

DI Thomson said of Mitchell: "He is completely devoid of any remorse or empathy, that's the thing I find really hard.”