When Boris Johnson resigned as foreign secretary on Monday, I was at my desk. As on many days over the past three years, events beyond my control meant I wouldn’t be able to go on working – the rest of the day would be spent fielding worried phone calls from Iran, and later from the press, answering through my disorientation what this might mean for my wife Nazanin.

Nazanin is the British charity worker who was arrested on holiday with our daughter Gabriella, and held in Iran for more than 800 days. She was convicted of secret charges at a trial where she wasn’t allowed to speak, called a spy during a propaganda campaign on Iranian TV, subject to a second court case which was blamed on Boris Johnson’s mistaken comments about her at a select committee – a case that was closed, and then reopened a couple of months ago.

Gabriella now lives with her grandparents in Iran, and I have been unable to visit her. Nazanin has been told explicitly by the judge that there is no crime in her file, but she is being held over a long unpaid UK government debt to Iran.

Many of those who follow our story have expressed disbelief – how can this be going on? Ordinary citizens are not supposed to pay the price for their government’s mistakes.

Given the impact of his actions on our case, it might seem surprising that we were upset by Johnson resigning. But in the weeks after his error, Nazanin became a high priority for Johnson, high enough to make him travel to Iran. He promised to leave no stone unturned. The concern was genuine, and Nazanin’s father has asked me to pass on the family’s thanks.

Even when things subsequently went quiet, we held on to that promise mentally – it was the rock on which we built our hope.

With Johnson’s resignation, it feels like that hope has evaporated.

After 800 days of setbacks, we continue to be anxious. Our frustrations with the government have been publicised. We fear a possible downgrading of our case. On the phone yesterday, Nazanin worried not just that the momentum had stalled, but that events had moved on and she would be forgotten.

Currently, our anxieties have a specific focus: we are awaiting a decision as to whether Nazanin should be granted diplomatic protection, which would allow greater pressure to be applied to the Iranian government.

Jeremy Hunt is the constituency MP of a number of my relatives and has been kept well informed of Nazanin’s case. He’s been made aware of the family’s frustrations and they have found him sympathetic, supportive and aware of human rights issues, while encouraging us to do whatever we need to do to bring Nazanin home, to not to be afraid to make noise. He has personally raised Nazanin’s case.

We therefore hope that this is a fresh opportunity – for Nazanin and the others you don’t hear so much about – to resolve things. While we might not make it into his in-tray on his first day (thanks to Donald Trump), we would hope to within his first week.

What would we like the new foreign secretary to do differently?

First, I would like to meet him – how soon that happens will be an indicator of the extent to which we are a priority.

Second, we want him to make a clear statement that he is committed to securing the release of British citizens such as Nazanin. There have been lots of stories recently about the small print of British citizenship, but on some things the government needs to take responsibility.

Third, he inherits a decision: is the government going to grant Nazanin diplomatic protection? We also want him to press for the British embassy finally to be given access to see Nazanin and check that she is OK. After two years, it remains a nonsense that this has not been allowed.

Finally, he needs to reach out to other countries whose citizens are also being arbitrarily held. This is an issue on which we must work with our allies, with colleagues in Europe and the US – starting with visits this week – rather than continuing to struggle to solve things on our own. Protecting British citizens means engaging with Iran’s legitimate demands, while challenging the abuse of arbitrary detentions.

I still have a pile of painted stones in our flat made to symbolise Johnson’s vow to leave “no stone unturned”. Gabriella likes to look at them on Skype. I have promised Nazanin that I will give Jeremy Hunt one when we meet, as a reminder of the promises he inherits with the job.

• Richard Ratcliffe is the husband of Nazanin Zaghari-Ratcliffe. He works as an accountant and lives in London. His campaign to free his wife can be contacted via @freenazanin