Nazanin Zaghari-Radcliffe, a dual British-Iranian citizen, has been in jail in Iran for the past 19 months on espionage charges that both she and her family vehemently deny.
Earlier this month, Johnson mistakenly told a British parliamentary committee that Zaghari-Ratcliffe was in Iran teaching journalists when she was detained. Her family and employer have always maintained she was visiting family on vacation.
The seriousness of Johnson's error became apparent days later when Zaghari-Ratcliffe was summoned to an unscheduled court hearing at which the Foreign Secretary's remarks were cited as proof that she had engaged in "propaganda against the regime."
Fears have grown that her five-year sentence could be lengthened.
Johnson later clarified his remarks, stating that she was in Iran on holiday, and apologized to Zaghari-Ratcliffe's family.
On Wednesday, Johnson met with the woman's husband, Richard Ratcliffe, for the first time and said the UK government was determined to bring about a lasting reunion for the family.
"I can tell you that people here in the Foreign Office and across government have been working very hard over the last 19 months to secure the release of Nazanin Zaghari-Ratcliffe and indeed to solve some other very difficult consular cases in Iran," Johnson said.
"And we're going to continue to do that and we will leave absolutely no stone unturned in our efforts to do that."
Ratcliffe, who has campaigned tirelessly for his wife over the past 19 months, said that the meeting was "positive and constructive."
He is also seeking to accompany Johnson to Tehran before the end of the year, but no arrangements were confirmed Wednesday.
During the meeting, Ratcliffe asked Johnson whether the British government would afford his wife diplomatic protection. But the Foreign Office had reservations about such a move, Ratcliffe said.
"Diplomatic protection is, in essence, when a state like Britain decides that Nazanin was being treated badly because she is British, and she is entitled to be protected as an extension of the British state. It is not unprecedented, but it is a big step," he told a news conference.
"I said I thought it would be important and helpful. The Foreign Secretary and the Foreign Office expressed reservations, and we agreed that there are some questions that we have sent from the lawyers."
"They have agreed to answer the questions and then for the lawyers to sit down and talk it through, both legally and then also practically."
Ratcliffe also spoke of his pain at not being able to see his three-year-old daughter Gabriella, who was with Zaghari-Ratcliffe when she was detained in April 2016. Gabriella was placed in the care of Zaghari-Ratcliffe's parents in Iran.
He is now hoping to have both of them back in Britain for Christmas and for Zaghari-Ratcliffe's birthday on December 26, especially, he said, with his wife's health suffering.
Last weekend she was examined by a specialist after finding lumps in her breasts, said Ratcliffe, who also has concerns about his wife's mental wellbeing.
"She talks about being on the verge of a nervous breakdown," he told the news conference Wednesday. "I absolutely believe that's true. I think it's important I don't exaggerate anything in the media and I'm not melodramatic, but she is in a difficult place."