Helena Bonham Carter hired a psychic to contact the late Princess Margaret before playing her in The Crown.
The 52-year-old actress enlisted the help of a clairvoyant to speak to Queen Elizabeth's sister - who died in 2002 aged 71 - from beyond the grave to ensure she researched the role with "as much depth as possible".
A TV insider said: "She always likes to research her roles with as much depth as possible - and is always prepared to go that extra mile.
"So if that means using someone with supernatural powers to speak to a character who is now on the other side then Helena has no problems with doing that."