Harpenden serial killer Joanna Dennehy is the only female murderer who dominated her accomplices, according to a leading criminologist.

Professor David Wilson said Dennehy’s case contrasts all other examples of relationships between killers, including Myra Hindley and Ian Brady and even Fred and Rose West.

A Channel 5 documentary into Dennehy aired last night, almost a year after she was jailed for butchering three men in cold blood blood in Peterborough. 

The former Roundwood Park School student boasted she murdered Lukasz Slaboszewski, 31, lover Kevin Lee, 48, and John Chapman, 56, “to see if I was as cold as I thought I was”.

Unsatisfied, she then drove across the country with hulking 7’ 3” Gary Stretch and attempted to kill two dog walkers at random in Hereford.

Professor Wilson said in the episode last night: “It’s not unusual for a killer to have an accomplice. We’re all familiar with infamous male and female killer couples.

“The psychology behind this relationship is called a ‘folie a deux or a madness shared by two’ and one of those two, usually the man is dominant and the other subservient.

“What’s unusual in Dennehy’s case is that she’s the dominant one and men are doing her bidding.”

Dennehy was born in Harpenden and attended Roundwood Park School. The 32-year-old left her family’s £315,000 four-bedroom home in St Albans at 16 after she had begun bunking school and drinking heavily.

The episode, which is the first documentary film to examine the case of Dennehy, was part-filmed in Lybury Lane, Harpenden, and also featured an interview with Dennehy’s former partner – John Treanor, the father of her two children.

John met Dennehy in 1997 when she was 15 and a year later they moved to Luton.

Treanor expressed his horror at the crimes committed by Dennehy and the impact it will have on the victims’ families and his own children.

Professor Wilson said growing up, Dennehy was a normal happy child. She excelled at school and sports and her parents dreamed that she would end up at university studying law.

That she became responsible for the horrific murder of three men in the space of ten days shocked those around her.

The new documentary series focuses on the cases of seven notorious, cold-blooded psychopathic killers, and will continue next week.