There was a time, unlikely as it seems now, when people were quite excited by the prospect of Karen Bradley as Northern Ireland Secretary.

After a year of drift under James Brokenshire, officials on both sides of the Irish Sea credited her with injecting a new sense of energy and purpose into stuttering talks to restore the Stormont executive.

“She speaks human,” was one approving reflection from the Northern Ireland Office on the personable Bradley’s direct, informal style, a marked contrast with Brokenshire’s more deliberative approach.

That was in February. Seven months on from her appointment, and 19 months on from its collapse, there is still no executive in Belfast, nor anything in its place. Any goodwill that Bradley won in her honeymoon period has evaporated.

In increasingly desperate political times, that capacity for speaking human is now a liability, rather than an asset. Bradley has holed her own credibility below the waterline by admitting in an interview with the House Magazine that she did not know that Northern Ireland voted along constitutional lines when she was appointed, a fact so basic that it would be overkill to include it in newspaper copy.

It’s a startling admission that raises any number of equally discomforting questions (here’s one: who did Bradley think the DUP were when they agreed a confidence and supply deal with her government last June?). One Whitehall source describes it as “an astonishing thing to say to a journalist...you don’t advertise you were completely clueless about basic facts before you took the job on”. And despite its underlying good intentions, it provides yet more fodder for those who believe, with some justification, that English politicians know nothing of Northern Ireland.

But the real political lesson to draw from this doesn’t concern Bradley, but Theresa May. That the former is in her job in the first place illustrates the prime minister’s preference for patronage over suitability when it comes to appointing ministers. Bradley was appointed not because she was the best fit for the Northern Ireland Office — which might have been a consideration given Brexit and the lack of an executive — but because she was trusted May lieutenant from her days as Home Secretary, as was Brokenshire.

You might argue that this is no different from any appointment made by any prime minister ever. Add to that the lowly status Westminster accords to the Northern Ireland brief — David Cameron treated it as a dumping ground for ministers he didn’t like but couldn’t dispense with — and that argument seems a strong one.

Tory MPs, however, would argue differently. Many are frustrated by the stasis at government’s top table, which they see as congested with mediocre performers in important briefs, and want a radical reshuffle. Bradley’s continued presence despite her objective failures in her post illustrates why they won’t get one.

The government has no real domestic vision beyond surviving, so when it comes to ministerial vacancies, May and the whips employ a whack-a-mole approach rather than any strategic thinking.

Holes are filled with friends of Theresa, regardless of suitability. The most egregious example as far as many Tories are concerned is the replacement of Michael Fallon at defence with Gavin Williamson, May’s former chief whip, but less high-profile examples animate MPs too. When Greg Hands resigned as international trade minister in June, he was replaced by George Hollingberry, a ministerial novice whose only claim to promotion was his position as May’s parliamentary private secretary.

The one case where the prime minister didn’t promote a friend — the appointment of Sajid Javid as Home Secretary — shows why she sticks to this rule. Javid has spent his four months in the job ripping up May’s legacy while someone like Bradley, who government loyalists recall with some relief was the prime minister’s preferred choice, would have dependably tread water and posed no threat.

For that reason, names like Karen Bradley will always be first on May’s teamsheet for as long as she is prime minister. They are each other’s political life support machines: the prime minister cannot survive in office without the insulation of her loyalists, of whom few would retain their posts under another leader. For now, it will take gaffes even more astonishing than Bradley’s to displace them.