Kenneth Branagh's recent film versions of two Agatha Christie novels remind me of former Conservative Prime Minister David Cameron's speech in favour of gay marriage at his party conference in 2011.

Cameron, now UK Foreign Secretary, drew loud applause from delegates when he said: "I don't support gay marriage despite being a Conservative. I support gay marriage because I'm a Conservative." His Marriage (Same Sex Couples) Act 2013 duly cruised through a House of Commons packed with sexual revolutionaries. 

Cameron took an institution that belonged to Christian Britain - life-long, monogamous, heterosexual marriage - and redefined it in a way that embraced the 1960s sexual revolution.

Branagh seems to have done a similar thing with Agatha Christie (1890-1976) in his films based on two of her books, which he directed and in which he played her celebrated Belgian sleuth Hercule Poirot. He has taken a feature from Christian Britain and remoulded it in the image of the permissive society.

Christie was a writer with a committed Christian faith who made Poirot a Roman Catholic Christian. Writing in 2009 in First Things, the American religion and public life magazine, Yale University historian Nick Baldock shed light on "the Christian world of Agatha Christie". 

He wrote: "Christie was baptized into the Church of England, although her peripatetic mother dabbled in other religions, including Catholicism, and introduced Agatha to the possibilities of occult spirituality, a theme that recurs in her stories outside the classic detective genre. Nonetheless, it was her mother's copy of The Imitation of Christ that Christie kept by her bedside."

Inscribed on the flyleaf of her copy was a quotation from Romans 8 beginning: 'Who shall separate us from the love of Christ?" Baldock recorded that at Christie's memorial service in 1976, her publisher William Collins shared this as "a reflection of the gentle Christian spirit that resided within her".

Baldock also observed: "The sleuth, as bringer of truth and dispenser of justice, is always to some extent an agent of God and Poirot was given to addressing le bon Dieu with a degree of familiarity. Occasionally he was more serious, as in Cards on the Table, in which he notes that a man 'imbued with the idea that he knows who ought to be allowed to live and who ought not' is 'halfway to becoming the most dangerous killer there is—the arrogant criminal who kills not for profit—but for an idea. He has usurped the functions of le bon Dieu'."

Branagh's 2022 version of Christie's 1937 novel, Death on the Nile, turns two of the characters, originally a wealthy woman and her nurse cum bag-carrier, into a lesbian couple, played by the comedy duo, Jennifer Saunders and Dawn French.

Branagh's Death on the Nile also has the principal female villain at the beginning of the film boasting about the amount of pre-marital sex she has been having, words that Christie would never have dreamed of putting into the mouth of one of her characters and absent from the 1978 film version of her novel, with Peter Ustinov as Poirot.

Branagh's 2023 film, A Haunting in Venice, loosely based on Christie's 1969 novel, Hallowe'en Party, puts Poirot in Italy just after the end of World War II and subjects him to a fate that Christie never did. Branagh has him losing his Christian faith and giving a crass justification for his apostasy.

Branagh's Poirot declares: "If there is a soul, there is a God who made it and if we have God, then we have everything - meaning, order, justice. But I have seen too much of the world, countless crimes, two wars, the bitter evil of human indifference, and I conclude, no - no God." Christie's Poirot, by contrast, took a more rational view of the evil we human beings do and rightly refused to blame it on God.

Why won't the likes of Cameron and Branagh leave Christian Britain alone and create their own institutions and characters? Perhaps they recognise quality when they see it and want to hand these legacies on to the next generation but adapted to a form that Millennials and Generation Z can accept? Or perhaps they lack the imagination to make their own original 'progressive' creations?

But the result of trying to take features from Christian Britain and make them politically correct is precisely the pit Branagh's Poirot fell into over his loss of faith – absurdity. Christie would never have had her Poirot saying anything so absurd.

Julian Mann is a former Church of England vicar, now an evangelical journalist based in Lancashire.