Harpenden serial killer Joanna Dennehy is still trying to lure men from inside her cell, according to a new ITV documentary airing tonight.

Herts Advertiser: Dennehy jovially sticking her tongue out as she brandishes a jagged knife with handcuffs attached to her trousers.Dennehy jovially sticking her tongue out as she brandishes a jagged knife with handcuffs attached to her trousers. (Image: Archant)

The murderer, who grew up in the town and attended Roundwood Park School, killed three men over 10 days in March 2013.

According to the programme, Dennehy continues to manipulate men and has even had a wedding proposal since being jailed.

The ITV documentary is hosted by Susanna Reid who investigates how the killer is behaving from inside HMP Bronzefield, Surrey.

A source told the Mirror: “She’s been writing her book for ages and reckons it will be made into a film.

“But it is not really a book – it is just pages of her sick fantasies that only make sense to her.”

The St Albans-born killer is reportedly seen laughing and flirting with male police officers in a police station minutes after being arrested.

She is one of only three British female murderers who will die in jail.

The programme is on ITV tonight at 9pm.