What would Mr Bates say?! Downton star Joanne Froggatt impresses as a serial killer in Dark Angel

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Downton Abbey star Joanne Froggatt is no stranger to period dramas but her latest one could not be more different from the show that made her household name.

The actress, who played ladies' maid Anna Bates in ITV's hit series Downton Abbey stars the sinister role of a Victorian poisoner for two-part drama Dark Angel, which is based on historical events.

Dark Angel Joanne Froggatt
Joanne Froggatt plays Mary Ann Cotton (ITV)

Jo, 36, plays Mary Ann Cotton, a poverty-stricken woman living in north-east England in 1857 who committed a series of grisly murders to bolster her finances and boost her social standing.

Her victims included her husbands and even her own children as she used tea laced with arsenic to make a more comfortable life for herself by claiming life insurance policies and viewers were shocked at the contrast between Joanne's roles.

Dark Angel
Jona Armstong with Joanne in Dark Angel (ITV)

She even delivered on the North East accent.

But it did make everyone at home nervous to drink tea.

Even The Only Way Is Essex star Amy Childs was hooked.

The two-parter was inspired by David Wilson's book Mary Ann Cotton: Britain's First Female Serial Killer, and was filmed in County Durham and North Yorkshire.

Dark Angel airs on ITV at 9pm and concludes on November 7.