The trailer for brand new documentary series Paranormal: The Girl, The Ghost and The Gravestone has been released alongside the key art. The series is a co-commission between BBC Three and BBC Wales.

In this gripping new box-set series, Radio 1 presenter Sian Eleri investigates a seemingly ordinary farmhouse in north Wales which, in the late 1990s, was widely considered the most haunted house in Britain.

The story made local and national headlines as the family who lived at the farm became ever more desperate in their search for answers. More than 300 apparently paranormal events were documented at the house in video footage, audio interviews, photos, and eye-witness accounts – all of which had been locked away, until now.

Reports ranged from words and pictures appearing and disappearing on the walls; objects moving around the house; and multiple witnesses reporting seeing a hooded figure and the ghost of a girl rumoured to be buried in the garden.

With exclusive access to the case archive and to those at the heart of the case, Sian sets out to uncover what really happened at Penyffordd Farm. She starts out as a sceptic, but in a series of chilling and increasingly bizarre twists and turns, Sian is left questioning everything she thought she knew.

Paranormal: The Girl, The Ghost and The Gravestone is produced by Twenty Twenty Productions Ltd for the BBC. Series Producer is Hugo Pettitt and Series Director is Rory Jackson. Executive producers are Ruth Kelly and Jo Hughes. It was commissioned by Clare Sillery, Head of Documentaries at the BBC, Fiona Campbell, Controller of BBC Three and Young Audiences and Nick Andrews, Head of Commissioning for BBC Wales. The Commissioning Editors are Max Gogarty and Sian Harris.

Paranormal: The Girl, The Ghost and The Gravestone starts on BBC Three on 15 August with a double bill with episode 1 at 9pm and episode 2 at 9.30pm and all episodes will be available on BBC iPlayer. It will also air on BBC One and BBC One Wales on 16 August at 10.40pm.