Richard Ratcliffe, her British husband, an accountant who lives in north London, has appealed to the Foreign Office to raise her case during a visit to Tehran this week. He hopes that the Foreign Office minister Alistair Burt will hold talks with senior Iranian politicians about his 38-year-old wife, a charity worker. Burt is meeting Zaghari-Ratcliffe’s family, and is due to attend the official swearing-in ceremony for the re-elected president, Hassan Rouhani, on Saturday.

Zaghari-Ratcliff has decorated her cell with pictures from her infant daughter, who is now three. The child had her passport confiscated, and is living with her grandparents in Iran. She is allowed to see her mother twice a week.

Ratcliff, 42, talked about his wife’s situation, “It’s one of the quirks of the law and UK policy about dual nationality. Nazanin lives in Britain, she is British, her job’s here, her home is here. She is being held in part, or mainly, because she is British. The way in which you can’t do anything about it because she is Iranian seems so counter-intuitive.”

Zaghari-Ratcliffe was arrested at Tehran airport as she tried to leave the country at the end of her visit. She was accused of trying to topple the Iranian regime. “Iran hides behind dual nationality,” said Ratcliffe. “The reason they don’t allow the British ambassador access to her is because, ‘Oh, she is Iranian,’ which is a fiction, because the reason they took her is because she is British.”

Ratcliffe has applied for an Iranian visa and is hoping to visit his daughter, Gabriella, as well as his wife.

“I have promised Nazanin I won’t do anything with Gabriella without her agreement, because of course the only thing Nazanin lives for at the moment is visits from her daughter. That is the worst thing at the moment, missing these months with her daughter.”

In Evin prison, Zaghari-Ratcliffe is suffering from mental health problems, as well as physical issues with her shoulder, neck, eyesight and teeth.

Of his recent meeting with Burt, Ratcliffe said, “He was kind. It feels like he cares. I do have a dispute with the Foreign Office that they are not pushing hard enough, and I have made that clear all along, but I do not doubt that he cares.” Labour MPs have criticised the lack of progress. However, Ratcliffe said he remains hopeful that his wife will be released, but said Foreign Office involvement would be critical. “The Foreign Office are never optimistic,” said Ratcliffe. “They are just guarded.”

About his upcoming trip, Burt said, “We hope to build further on improving UK / Iran relations during President Rouhani’s second term. “The president’s personal commitment to the nuclear deal is welcome and it is vital both our countries work closely together to ensure the deal continues to be successfully implemented. We are also keen to maintain dialogue on Iran’s regional policies, human rights and particularly our dual national detainees. Progress in all of these areas is important to the UK.”