Downton Abbey's Joanne Froggatt to play real life serial killer in Dark Angel

Downton Abbey star Joanne Froggatt has signed up to appear in another period drama – playing a real-life serial killer.

The actress, who plays lady’s maid Anna Bates in the hit ITV show, will play Victorian poisoner Mary Ann Cotton in a two-part drama called Dark Angel.

Cotton was hanged after being convicted of killing three of her husbands, though some historians estimate she may have had more than 20 victims.

Joanne Froggatt (Andreas Branch/AP)

ITV’s controller of drama Victoria Fea, who commissioned the show, said it was 'an extraordinary and chilling true story'.

She said: “We’re delighted to have an actress of Joanne Froggatt’s calibre in the lead role.

“The combination of a tautly-written script, an outstanding cast and great producers in World Productions make this a really exciting addition to the ITV drama slate.”

Filming on the show, in north Yorkshire and County Durham, starts in August.