If Theresa May can't take a joke about her £1,000 leather trousers, how long can she last as Prime Minister?

This is not a question anyone can have expected to be addressing so soon, but is Theresa May starting to crack? Perhaps that overdramatises some minor manifestations of the pulverising stress she is under. Yet, for someone with an image built on strength and what passes in political circles for sanity, the Prime Minister does seem alarmingly determined to undermine her own brand.

Paranoia is a natural state of mind for leaders facing their political death. When a fading PMs detect plots everywhere, that’s because every cabinet piranha scents their blood.

It’s when a strong leader is inexplicably insecure that you worry. May is already being compared to Richard Nixon, who was highly popular and guaranteed a second term when he suicidally overegged the re-election pudding with Watergate.

May is the only Westminster figure with a healthily positive approval rating. She holds an embarrassingly huge poll lead over Labour and seems assured a landslide whenever she goes to the country. Yet when she ought to be playing cuddly, chilled out Claudio Ranieri, her inspiration is Jose Mourinho, the paranoiac’s paranoiac who publicly lacerates his players for betraying him.

Admittedly, Boris Johnson’s remarks about the Saudis offended against diplomatic etiquette by being the plain truth (and God love you, Boris, for that). But as the coach who hired him, May’s regular acidic critiques of her star striker reflect much more, and much worse, on her judgment than on his.

More disturbing was the recent attempt to ban Brexit-related leaks. Strong leaders, while infuriated by it, grudgingly accept that leaking is inevitable and essential to the health of the body politic. Leaking is democratic goverment’s lymphatic system, draining away the toxic secretiveness that creates the malignant scandal of tomorrow when allowed to store up.

A week after a Downing Street “confidential memo” outlawing leaks was leaked to the Mail on Sunday, that paper has another leak about a sexist and memorably babyish No 10 counterstrike against Nicky Morgan, whom May sacked in July. The pro-Remain former Education Secretary’s offence was to highlight the £995 cost of May’s leather trousers by Amanda Wakely. Morgan sniffed that the Conservative Party had noted this, and that she never spent that kind of dough on anything but her wedding dress.

May overreacted violently by unleashing Fiona Hill, her joint chief of staff and chief attack dog. Hill texted Alastair Burt, another Remain stalwart who accompanied Morgan to a previous No 10 meeting about Brexit: “Don’t bring that woman to Downing Street again.”

On hearing this, “that woman” (yeucch; who talks like that?) messaged Hill: “No man brings me to any meeting.” Hill responded: “Well he just did. So there!” Of course one admires the delicate wit of “so there!”, even if “nurgh nurgh nurgh nuurrrrrgggghhhh nurgh!!!” might have had the more dazzling Wildean thrust.

You can guess why Theresa May is hypersensitive about fashion. Her love of clothes is almost the solitary glimpse into her private personality she’s allowed us so far, the only frivolity with which to leaven the grinding tedium of her swottish persona. So no wonder she is prickly when it used not to humanise her, but to make her look extravagantly out of touch with the “just about managing”.

But allowing her irritation to escape and spark a fifth-rate catfight was both a trivial and a serious mistake. Clearly, such a banal incident will soon be forgotten. Equally obviously, you should no more reveal a weakness in combat politics than in the mafia. This seems a loose equivalalent of his fellow mobsters discovering that Tony Soprano was seeing a shrink.

To reveal such brittleness about something so minor hints at deeper and more dangerous insecurities. It makes you wonder whether May is psychologically unsuited to being PM on the template of Gordon Brown, who also had a successful, record-setting stint at a great office of state before spectacularly failing to adapt to the demands of the top job.

Like Brown, May has taken to replying to simple questions with irrelevant gibberish. Asked about the trousers during last week’s ingratiation session with the Saudis, she said: “I believe it is important for politicians to get out and about, and that’s what I continue to do.” That suggests that sustained physical movement is impossible in anything but leather trousers retailing at a fiver under a grand. Which may explain why so many women who only own jeans and dresses are barely managing. They can’t get beyond their own front doors. A confident prime minister would have laughed it off, ridiculing the dull puritan implication that a successful woman doesn’t have a perfect right to spend her money as she pleases in support of the fashion industry. Only a desperately nervous one would do the full Peggy Mitchell, with “Right, Morgan, you slaaag. Aaahht! You’re barred!”

This is not a good time for peevish, vindictive leadership. The country will need nursing through the years ahead by someone willing to answer much tougher questions than the one posed in Bahrain in intelligible English, and able to project calm assurance when internally sick with worry.

It’s still early doors for Theresa May, who retains an unusually large dollop of goodwill. But if she carries on sweating the tiny stuff, slapping down colleagues and obsesssing about leaks, the misplaced insecurity could become a self-fulfilling paranoia. She needs to start growing into her prime ministerial trousers, and quick.