For a split second I presumed Barak Obama was the president caught visiting his mistress.

I was incredulous. "The fool," I thought. "He's finished." Then the newscaster said it was Francois Hollande, making it a different affaire entirely.

The French, as we have been reminded this week, are very grown up about sex. It is firmly, in their minds, a private matter even for their president. When they were polled, 77% thought it was not the public's business and 88% said it did not affect their opinion of him.

Steven Camley's cartoon

I was impressed. Clearly the French really do offer their public figures the privacy and respect they would give their friends and neighbours and the discretion they would ask for themselves. We could learn a lot, was my initial response. Several days later I'm wondering: is it that simple?

If a public figure has been revealed to be breaching commonly held standards of personal morality, can the matter remain one of public indifference? More importantly, should it?

The devil, as always, is in the detail and in this case there's already too much for the privacy argument to have much force. If Francois Hollande was a private citizen his cheating on one girlfriend with another would be his business. But he is the president of his country and his partner, Valerie Trierweiler, is the First Lady of France.

She lives in the Elysee Palace at public expense. She has an office and a staff of five or six. Last week she returned from distributing French money to charities in Africa. She hosted a screening of a biopic on Yves Saint Laurent attended by the glittering and the great. She is scheduled to be the president's consort on a visit soon to Washington.

On Friday she was hospitalised suffering from "a severe case of the blues" after her partner's unfaithfulness was exposed by Closer magazine. In the context of the role Hollande has given her, the president's claim of privacy is weak.

What about the security guard who accompanied the president on a scooter to his assignations? He is a public servant paid for by the public purse. Should he be required to keep personal secrets that might breach his own code of conduct? Should he be sent for croissants for the lovers' breakfasts, as he was?

When his employer makes those sorts of demands, is that a private matter? I don't think so.

Then there is the security aspect itself. There are rumours that the flat where Hollande met the actress Julie Gayet is owned by a man with mafia connections. Even if that proves false, wasn't Hollande taking risks with his security?

That is the trouble with public figures claiming privacy. The more we know, the more questions there are about matters of legitimate public concern. Hollande is a bachelor who had a 30-year relationship and four children with Segolene Royal. That relationship overlapped with his long- standing affair with Valerie Trierweiler. Voters knew this when they elected him. They can scarcely be shocked when it becomes clear that he hasn't changed his habits.

After all, Hollande is a graduate of the old ways. He was a friend of Jacques Chirac who reputedly had multiple assignations while in office. Giscard d'Estaing was also a womaniser and Francois Mitterand, for whom Hollande worked as a junior aide, famously had a second family. The French press looked the other way. Their readers would have expected nothing else.

But the former presidents didn't install a mistress as First Lady and then publicly humiliate her. They didn't (or they weren't caught ) looking undignified on the back of a scooter on their way to clandestine trysts.

They weren't exposed being self- indulgent, abusing the public purse and possibly bringing the office of president into disrepute at a time when the country was on its economic knees. This might be dismissed as froth or frivolity at a time of economic plenty but life is hard in France at the moment. We've been going through a tough time too so we know what it's like. France is worse off than we are. More than 10 percent of the working population is unemployed; that is more than three million people.

Do they have a right to know whether their president is focused on pulling France out of its malaise? Is the story in the public interest? In my opinion, it is. What at first looked like a comic episode, truly a French farce, has become something more serious.

First, it is clear that a sophisticated attitude doesn't spare the French emotional pain. Trierweiler may be the-biter-bit but her situation is unenviable. Hollande has exposed her by his behaviour.

Secondly, and more importantly, he has demeaned his office by indulging himself while his countrymen should expect him to be committed only to delivering France from recession.

If Nero fiddled while Rome burned, Hollande philanders. And on the cusp of that trip to Washington, does their president's behaviour make him a figure of international ridicule?

It was in America three years ago that the private practices of Dominic Strauss-Kahn brought his high-flying career to a crash landing. Then head of the International Monetary Fund, Strauss-Kahn had ambitions to be a future French presidential candidate.

After a New York chambermaid accused him of rape, several French women broke cover to say he had also been sexually forceful with them.

It started a national discussion in which French women began to re-examine their country's long- standing tolerance of sexual dalliances. Some queried whether it benefitted only men. They called for a re-think of values that left some of them feeling vulnerable and ill-used. In his defence, Hollande might point to his bachelor status. Clearly that is no excuse in today's culture.

Betrayal is betrayal inside marriage or out. Royal, the mother of his children, is regarded as his first wife. For Hollande's career, is actress Julie Gayet a mistress too far?

It matters for the individuals concerned. It also matters for France.

Hollande is scheduled to hold his first press conference of 2014 today. He is expected to re-launch his presidency by outlining plans to boost the flagging economy.

He has spoken about "abuses in the welfare system" and of "doing more by spending less". As we know from experience that involves bitter pills to swallow.

Will the electorate have confidence in their president if they think his mind is on earthier matters? A man who can't even run his household is unlikely to inspire confidence in his country, or in the wider world.

Does that cartoon image of a small, plump, ageing man, riding pillion on the back of a scooter to risk all for a night of sex with his mistress inspire you with confidence? Are the voters of France better off knowing about it than not?

In my opinion, they are. Privilege always likes to cloak itself in privacy. In Hollande's case, the cloak has been ripped away. What has been exposed is Hollande's weakness as a man and as a president. I think this has done France a public service.