It is treachery that drives the plot of A Very British Scandal — the BBC’s new drama which depicts the marriage and divorce of Ian and Margaret Campbell (Paul Bettany and Claire Foy), the 11th Duke and Duchess of Argyll. A disclaimer by the screenwriter, Sarah Phelps, warned that some events were created or changed for dramatic purposes.

“Never trust a Campbell” is a saying amongst Scots. It refers to the Glencoe Massacre of 1692, whereby Captain Robert Campbell ordered his men to murder their hosts, the MacDonalds. It was murder under trust, a murder of those who had shown them kindness.

Since her birth in 1912, Margaret Campbell was conditioned to the cruelties of the world: an emotionally abusive mother who mocked her stammer, an abortion in her teens, a stillborn baby, eight miscarriages and two failed marriages. Like most women, she buried her trauma and moved on.

Some viewers mistook Margaret as a gold-digger who was lured by Ian’s promise of treasure from a shipwreck, to which he had salvage rights. An heiress to the Celanese Corporation, she didn’t need the money and was attracted to the status of being a duchess. She and Ian used the alleged treasure (to this day, none has been found) to encourage her father George Whigham to write cheques for Inveraray Castle, the Argyll family seat.

The first cheque of £100,000 was to repair the roof and further cheques followed to the figure of £250,000. A self-made man whose in-laws looked down on him, George’s patronage of Clan Campbell was validation of his place in noble society.

Likewise, in aristocratic circles, Margaret was a foreign species amongst the English roses. She was a Glaswegian raised in New York. Perhaps as a nod to Margaret’s non-U origins, Phelps had Margaret say “dessert” and not “pudding”. The noblesse oblige of Twitter erupted: no aristocrat would say dessert. That’s the point: Margaret was an outcast.

Before Margaret committed to Ian, she was seeing Roberto Caracciolo, 11th Duke of San Vito. She sent both men a telegram: “Bored and missing you. Wish you would come to London.” Roberto declined; Ian came and proposed a week later. It was a whirlwind romance, but Ian needed her money.

At that moment, Margaret realised she had been swindled

Both Sarah Phelps and Claire Foy wanted to demonstrate Margaret’s unlikeable qualities.  For example, Margaret forged letters questioning the paternity of Ian’s sons. Vanity Fair’s obituary of Margaret called her an “an absolute demon” and indeed Ian’s children considered her a Hecate of the Highlands, with the keys to their castle. Ian’s daughter, Lady Jeanne Campbell, the future mistress of Sir Oswald Mosley, had no love for Margaret and helped Ian to steal her diaries.

The scene between Ian’s former wives, Janet and Louise, and then Janet and Margaret, said so much without divulging their experiences with Ian. In time, they would share a common bond of having been used and abused by him.

In reality, Margaret was the antagonist in several legal battles waged by Louise Campbell and Yvonne MacPherson. The Bastardy Case was thwarted by Louise, who sued Margaret for libel and slander. Louise received £10,000 in damages and a court injunction, preventing Margaret from discussing the matter.

Later, Ian informed Louise that Margaret had broken the injunction by speaking of their sons, and so Louise’s lawyers sent an application to Mr Justice Paull for Margaret’s committal to Holloway prison.  Luckily for Margaret, the hearing had gone in her favour.

Margaret had also forged a telegram from Yvonne to Ian, implying they were having an affair. Yvonne sued Margaret for libel and slander and received £5,000 in damages. “Now Margaret will eat humble pie,” Ian told George Whigham. Afterwards, George closed his cheque book.

The greatest blow for Margaret was an injunction banning her from entering Inveraray Castle. At that moment, as portrayed by Foy, Margaret realised she had been swindled. In real life, she broke into the castle and smashed Ian’s records and stole his boomerang — the actions of a spoilt child, rather than a scorned woman.

Ian’s attempts to destroy Margaret would be considered illegal today. At first, Ian attempted to have Margaret certified insane due to a head injury from 1943. She had damaged her olfactory nerve which controls one’s taste and smell, but it had not impaired her judgement or made her a nymphomaniac. If successful, he would have had control of her finances.

It asks the question: was the system biased against women?

The series showed Ian breaking into Margaret’s bureau, where all of her evidence was conveniently stored. In fact, he gathered his evidence over a period of time and used a locksmith to break into her London home, where he ransacked it for evidence. Behind a bookcase, he found the Headless Man Polaroids, taken with Joe Thomas, a banker from Lehman Brothers, to whom she was engaged before meeting Ian.

The scandal of the Headless Man wasn’t his identity, but the means by which Ian had gathered his evidence. Today, he would receive two years imprisonment for stealing her images and exhibiting them without her consent. It raises the question: was the system biased against women?

Perhaps forgotten by the public was the 1923 divorce case of Russell v Russell, in which the Hon. John Russell, (later Baron Ampthill), accused his wife Christabel of adultery and rejected his son and heir. Their marriage was unconsummated and Christabel claimed to be a virgin, citing a medical report as evidence, explaining she had conceived via her husband’s sponge. The scandal led to the enactment of the Judicial Proceedings (Regulation of Reports) Act of 1926 to prevent detailed evidence in divorce cases appearing in newspapers. Or, in short, to protect the aristocracy. But who was protecting Margaret?

At the time of the divorce hearing at the Edinburgh Court of Session, Margaret was aged 51 and a grandmother. In terms of female ageism, society found it grotesque that a woman of her age had an active sex life.

In the series, Margaret is defiant as Lord Wheatley (a member of Clan Campbell) delivered his damning report, labelling her a sexual deviant. Whereas, in fact, Margaret was in Paris with her boyfriend, Bill Lyons. At the end of A Very British Scandal, Margaret walks out of court, into the unknown.

Although persecuted by the Scottish legal system, she kept on living.