A new two-part crime drama 'Dark Angel' begins tonight (October 31) on ITV about Mary Ann Cotton, a woman labelled Britain's first serial killer. It's feared she used arsenic to murder as many as 21 people, including 11 of her own children, her mother and three husbands.
The two part drama tells how Cotton, who was originally from Houghton-le-Spring, set about poisoning her victims with arsenic over an eight-year span in an attempt to benefit from insurance money.
Arsenic at the time was an easily bought and versatile household product used to disinfect bedding, cure warts and even smooth wrinkles. In powder form it could be put into tea or other items of food or drink.
Among Mary Ann's victims were husbands - she married four times - and she was hanged in 1873 after being convicted of killing three of them.
Some suggest the number of victims could be as high as 21 and it is thought Cotton murdered her own mother and 11 of her 13 children.
Cotton was eventually hanged for murder in 1873 in Durham County Gaol.
Dark Angel (31st October at 9pm, ITV) stars Downton Abbey's Joanne Frogatt and was filmed in North Yorkshire and County Durham.
Watch Helen Pearson's report: