Unlike her first two screenplays, Gypo and Ruby Blue, which were written in prose format with a predominantly improvised dialogue, every line of dialogue in The Calling is scripted. She handed one scene to Brenda Blethyn and Rita Tushingham to edit down whilst in make-up, from a long eight minute sequence to just a three minute scene, not wanting to take the responsibility of cutting any of her much admired actress's lines.
Like her character, Sister Gertrude, Rita Tushingham truly is an avid Liverpool fan and has supported the football team since she was a child in Liverpool.
'Jan Dunn' and Elaine Wickham were introduced to Brenda Blethyn by Bob Hoskins when he brought her to the set of Ruby Blue. Jan pitched Sister Ignatious to Brenda - who said she'd been interviewed the day before and when asked if there is anything she'd like to do yet that she hadn't, she had said "play a nun in a closed order, so I don't have to learn any lines."
Dunn cast all her nuns before writing the screenplay specifically writing the characters for the ensemble cast of women. She is building a reputation for writing interesting characters for women.