Last year, American publishers Merriam-Webster grandly declared that the adjective "Kafkaesque" had become so over-used as to lose all its meaning.

They may be right, but when we consider the plight of British-Iranian national, Nazanin Zaghari-Ratcliffe, it is the first word that springs to mind.

Imagine Nazanin in April 2016, waiting to fly back from Tehran to her husband in London, fresh from introducing her young daughter Gabriella to her extended family. Suddenly, she is whisked away, held on unspecified charges, and five months later, with no evidence presented, sentenced to five years in jail for undermining the Iranian regime.

Her detention has been close to torture: separated from her daughter; held alternately in solitary confinement or in overcrowded cells; and interrogated under a hood. Her mental and physical health have deteriorated at an alarming rate: when not feeling suicidal, she rages at the injustice of it all.

What makes it all the harder is that – in theory – a negotiated solution between our two countries should be possible. After all, Iran has benefited from the normalisation of relations with Britain, and clearly needs our support against the belligerence of Donald Trump.

However, the hardliners who run Iran’s security forces and judiciary – those who actually control Nazanin’s fate – may feel the opposite. They would shed no tears about a return to open hostility to the West, a discrediting of the current reformist regime, and a resumption of Iran’s nuclear ambitions.

In that context, we have a diplomatic minefield to navigate in order to secure Nazanin’s release. Enter Boris Johnson.

Through sheer carelessness or incompetence, his testimony at the Foreign Affairs Select Committee handed a gift to the hardliners. By saying Nazanin had been in Iran “training journalists”, an utterly false statement, he provided what Iranian State TV described as “proof” of her “real plot”.

By her own husband’s account, Nazanin sobbed with frustration when told of the Foreign Secretary’s comments, knowing how the Iranians would exploit them. And sure enough, they immediately threatened to double her sentence, based on this supposed new evidence.

Any foreign secretary with a shred of decency would instantly have admitted their mistake, and apologised. Instead we got a week of bluster. His words, Boris claimed, had been “taken out of context”. He was only sorry if others had “misconstrued” them to cause anxiety to Nazanin.

But in any case, he said, there was “no connection whatever” between his words and the new legal proceedings against Nazanin, despite all the evidence to the contrary.

This was compounded when his friend, Michael Gove, popped up to defend Boris on the BBC and, unforgivably, insisted that we still “don’t know” why Nazanin was in Iran.

The hardliners in Tehran must have rubbed their hands.

Finally, I dragged Boris to parliament on Monday, and after an hour of pressure, he caved in, conceded his mistake, and apologised. Now, we can at last get back to the urgent business of securing Nazanin’s release, and hope that the damage done to her case is not lasting.

There has been much talk about whether Johnson should have to resign over this matter, or whether Theresa May considers him "unsackable". Regardless of that debate, one thing should be clear: if he keeps this job, he needs to work harder at it.

That means spending less time plotting and scheming and more time reading his briefs. It means thinking before he speaks, and learning to avoid these mistakes.

Like his sickening remarks about clearing dead bodies for golf courses in Libya. Or his gaffes over Kipling or Bullfighting or talking to a Sikh audience about whisky exports.

If those episodes didn’t do it, I hope this one will finally bring home to him that you can’t do a job like foreign secretary on the hoof. And if you try, you won’t just damage Britain’s diplomatic relations and undermine our interests abroad; you will ultimately put people’s lives and freedom at risk.

So after a week of obfuscation, he was right finally to admit his mistake over Nazanin. But the real question for his future – let alone hers – is whether he is now going to learn from it.