Until I Kill You viewing figures uncovered as it delivers huge shock to ITV

The series based on a true story is currently tracking as one of ITVX’s biggest-ever dramas.

Until I Kill You has been airing on ITVX and the harrowing true crime drama tells the story of how Delia Balmer (played by Anna Maxwell-Martin) survived a near-fatal relationship with murderer John Sweeney (Shaun Evans). ITV has just released the viewership figures and it is destined to be one of the network's most popular dramas in history.

The show comes second to Mr Bates v The Post Office, having drawn huge streaming audiences in its first week, with more than 10 million streams so far. The drama is based on Delia's chilling memoir, Living With A Serial Killer.

The stars were keen to highlight Delia's bravery and resilience during her traumatic journey through the police and criminal justice system as they attempted to prosecute Sweeney for his crimes. The four-part series received five-star reviews from critics, with many praising Anna's portrayal of Delia.

The Guardian's glowing review said: "This extraordinary portrait of Delia Balmer, who survived a relationship with the murderer John Sweeney, is that rarest of things – fearless TV that values viewers’ intelligence.”

Since the series first dropped on November 3, streaming hours have increased by nearly a third compared with the same period last year.

Many viewers had chosen to binge the entire series straight away, as all episodes were added to ITVX at the same time.

The series was followed by a companion documentary featuring interviews with the real Delia Balmer, offering her the opportunity to tell her story directly.

Delia was working in London as an agency nurse in 1991 when she first met Sweeney in a local pub. Their relationship moved quickly and after Sweeney moved into her home, Delia started to see his dark side.

He committed a series of violent attacks on Delia, during which he admitted to murdering his ex-girlfriend, Melissa Halstead.

Sweeney was arrested but was granted bail and during this time, he subjected Delia to a near-fatal attack, which left her with life-changing physical and mental scars.

The serial murderer evaded capture for six years before returning to London, where he was arrested for the murder of another girlfriend, Paula Fields.

As Delia attempted to move on with her life, her fragile recovery was shattered again as she had to provide vital testimony against him in court.

ITV explained: "This is the story of one woman’s astonishing will to survive through physical and emotional torment, despite the failings of the institutions which were meant to protect her."

Until I Kill You is available to watch on ITVX