In recent years her hair grew longer and redder. As her bus pass approached, she grew more girlish. For those who hadn’t heard of Ulster’s First Lady before she mired herself in financial and sexual scandal, think Sarah Palin, Belfast-style.

She is, or was, a glamorous extrovert who (at the height of her secret affair with a teenager) declared homosexuality to be “an abomination” and suggested homosexuals could be cured by psychiatry.

Robinson and her husband Peter became known as the “Swish family Robinson” following disclosures that they received home £500,000 a year from the public purse – including £30,000 claimed in food allowances from Westminster over three years. A further £150,000 for constituency work went to four relatives, including their daughter and son. In their home, chandeliers abound.

When Iris decided on a political career, she did it with equal flamboyance. She joined Castlereagh Council, where Peter was leader; then became mayor; then an MLA (member of the Northern Irish Assembly) and a Westminster MP.

Then she broke the eleventh commandment. She got caught. The woman has been found in possession of a libido and a capacity for reckless infatuation. She took a 19-year-old Catholic lover. She arranged loans to set him up in business and didn’t declare them. She secured for him a council-backed contract and didn’t flag up her interest.

It smacks of small town corruption and it is the rope by which the province and her party will hang her – and her husband, the First Minister, if he is part of the cover-up. (Yesterday he stepped down for six weeks to allow an inquiry into his conduct.) But what Ulster can’t forgive is the sex.

It’s a political firestorm. And in the eye of it, there is Iris. Or is there? Where is Iris? No-one has seen her. No-one has spoken to her. She released a statement claiming depression, saying she is suffering a mental illness. Her husband says she is receiving “acute psychiatric care”.

Are we to think this middle-aged housewife turned politician is manic? That’s the shorthand in Belfast. And what excellent shorthand it is. It explains her inappropriate sexual relationship/s. It demonstrates her husband’s difficulty in controlling her. It excuses her questionable borrowing and lending and it prevents her facing the media.

Many powerful men across Northern Ireland must be sighing with relief that the loose cannon in their midst is jammed; for there is much more at stake here than one marriage – or even two careers. If the Democratic Unionist Party splits on this issue, Sinn Fein could form the largest party at Stormont, making Martin McGuinness First Minister. If that happens, hold on to your hat. It isn’t only the dissident IRA that’ll be back planting car bombs.

There is an Irish folk song that charts the tale of a woman led astray by a butcher boy. It’s chorus is: “I wish, I wish, I wish in vain, I wish I were a maid again, but a maid again I ne’er can be, till apples grow on an ivy tree.” It could be renamed Iris’s Lament. Little did she realise when her close friend, the affluent butcher Billy McCambley died and she fell into bed with his 19-year-old son Kirk, that she might bring the country down with her.

We have been told how she attempted suicide when her family discovered the affair. Was the failed overdose evidence of mental illness? Possibly.

But I wonder how a sane woman reacts when her family finds a sexually explicit letter written by her to a teenage lover? Iris knew that financial and political malpractice also lay undiscovered. This is a woman familiar with the high moral tone and thin tolerance of her husband, party and electorate; a woman who has trumpeted those values. In the heat of the night, with her hypocrisy about to be exposed, might the option of a sharp exit not seem sane?

I can’t answer that. I don’t know Iris Robinson. But I am troubled by a coincidence of “madness” in women whose behaviour inconveniences powerful men. It interests me that foolish Iris’s petty corruption is labelled mental instability, when all around her at Stormont sit men, apparently stable, whose pasts are littered with real skeletons.

We all grew up with Mrs Rochester locked in the attic. She is one of a trail of “mad” women in literature. As far back as The Woman in White by Wilkie Collins, a wife is committed to an asylum by her husband. He says of her that she is just mad enough to lock away and just sane enough to do him damage if she gets out. The recent best-seller The Suspicions of Mr Whicher, by Kate Summerscale, charts the real-life career of one of the first police detectives. It features a family where a father marries the governess, having had his first wife declared mad. Her children disagree with the diagnosis.

How many women down the ages were walled up in nunneries, asylums or until recently in Magdalene laundries? And how often was their “crime” sexual? Pregnancy was often the trigger, love for a man from the wrong class or the wrong tribe, same-sex relationships or an extra-marital affair.

The very word hysteria derives from the Greek word hustera meaning uterus. The medical condition was thought to be particular to women. In Scott Fitzgerald’s Tender is the Night, Nicole Diver suffers from it. It was triggered by an incestuous episode with her father when she was a teenager and he an adult – but she was the one removed from society.

But these days women are safe from false accusations of mental derangement, aren’t they?

On the night that Princess Diana gave her Panorama interview, she said Prince Charles didn’t want to be King; that he wasn’t cut out for the role. Within minutes, the Prince’s close friend, Nicholas Soames MP, was on Newsnight. “She’s unstable,” he said. It took my breath away.

More recently still, we saw Cherie Blair clatter through Downing Street with none of the quiet discretion of her predecessors. Cherie was mouthy, a political liability. Soon the suggestion circulated that she was “bonkers”. You don’t hear it now.

Yet ask yourself, when was the last time you heard a prominent man dubbed unstable? George III maybe? Is Tiger Woods thought batty for bedding waitresses across several states? Was Bill Clinton said to be mentally ill when he risked his presidency by cavorting with an intern in the Oval Office?

Iris Robertson is venal and greedy and very possible suffering the after effects of extreme hubris. None of that adds up to mental illness. You don’t have to be manic to fancy a fling. So let’s keep an eye on Iris. She is locked away from public view and will probably remain so for some time. But it’s important to ensure that no-one throws away the key.