British charity worker Nazanin Zaghari-Ratcliffe released from Iran, on her way back to U.K.

British-Iranian relations have been fraught in recent years, and there have been several stops and starts in negotiations over the British Iranians’ release. Their release comes after Britain settled a historic $524 million debt with Iran.

British Parliament member Tulip Siddiq tweeted a photo of Zaghari-Ratcliffe on an airplane and said that she is “now in the air flying away from 6 years of hell in Iran.”

“I am very pleased to confirm that the unfair detention of Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori in Iran has ended today, and they will now return to the UK,” Prime Minister Boris Johnson tweeted. Earlier in the day, he said that a negotiating team was at work in Tehran to free the British nationals.

The lengthy battle to free the detainees has been a high-profile one in the U.K. A BBC presenter choked up when announcing the news that two British nationals were heading to the airport to come home.

Zaghari-Ratcliffe’s husband, Richard, who has campaigned tirelessly for his wife’s release, told the BBC that after all the false dawns, he was waiting to see her in person. “Do we still quite believe it? I think when we see mummy, we will believe it,” he said, standing next to their 7-year-old daughter. He added that he liked the “big grin” on her face in the picture taken on the plane and that one of the things his wife was most looking forward to was a cup of tea.

Zaghari-Ratcliffe, a project manager with the Thomson Reuters Foundation, was given a five-year prison sentence in 2016 after Iranian authorities accused her of plotting to overthrow Iran’s government. She and her family denied the charges, saying she was on vacation with her daughter, visiting family in Tehran.

She spent almost five years in prison before she was released to house arrest at her parents’ home in Tehran.

In 2017, Johnson, who was foreign secretary at the time, was widely criticized when he said Zaghari-Ratcliffe was “simply teaching people journalism” before her arrest — a claim her family and employer vehemently denied. Johnson later distanced himself from his remarks.

Iranian authorities accused Ashoori, who spent almost five years in prison, of working for Israel’s Mossad intelligence agency, and Tahbaz, an environmentalist who was held for four years, of spying. They and their supporters deny the claims.

Iran’s state-run Fars News Agency, calling Zaghari-Ratcliffe a “spy,” said in a report published Tuesday that her release came after Britain agreed to unfreeze more than $500 million in Iranian funds and release an unnamed Iranian citizen imprisoned in Britain.

Britain and Iran have long been in talks over a debt of 400 million pounds ($524 million) that the United Kingdom owes Iran for not delivering tanks that Iran bought in the 1970s. Iran paid money to the International Military Services, an arms-trading subsidiary of the Defense Ministry. The U.K. canceled the tank order the Islamic Revolution in 1979.

Truss, the British foreign secretary, said that “in parallel” to the release of the detainees, “we have also settled the IMS debt, as we said we would.”

A sum of “393.8 million pounds has now been paid, which will only be available for humanitarian purposes,” she said in a statement to Parliament. “The repayment of the debt in parallel with the release of our nationals reflects steps taken by both U.K. and Iran to resolve issues of serious disagreement between our two countries,” she said.

Zaghari-Ratcliffe’s and Ashoori’s families have long claimed that they were being used as political pawns in a dispute over the debt, as well as for leverage in the talks over the Iran nuclear deal. The British government had previously said that the issues were not linked.

The developments come as talks in Vienna focused on an agreement to restore the 2015 Iran nuclear deal, which lapsed after President Donald Trump withdrew the United States in 2018, were put on hold last week after Russia made new demands related to the sanctions imposed as punishment for its invasion of Ukraine.

But on Tuesday, Russian Foreign Minister Sergei Lavrov said those demands had been satisfied by language in the existing text of the draft agreement, which diplomats had been hoping to adopt earlier this month. He added that Russia still supports the restoration of the deal, known as the Joint Comprehensive Plan of Action.

An exchange of prisoners between Iran and the West was expected to occur alongside moves to finalize an agreement, diplomats say. Those could include at least four U.S. citizens held in Iranian prisons and as many as 13 Iranians imprisoned in the United States.

There are still other outstanding issues to be resolved between the United States and Iran, which have been negotiating indirectly via intermediaries from the European Union, Russia and China.

One of the key issues from Iran’s perspective is a demand that the United States offer guarantees that no future president would be able to withdraw from the talks, as Trump did, according to a person familiar with the exchanges between Iran and the United States.

Such a guarantee is legally impossible for the United States to provide, but Iran may be coming around to the view that the deal may have to proceed without one, said the person, who spoke on the condition of anonymity to discuss sensitive negotiations.

The recent developments suggest that an agreement painstakingly negotiated over the past 11 months could suddenly come together soon, said Ali Vaez of the International Crisis Group. “Absent any unexpected development, they should be able to seal the deal in the coming days,” he said.

Kareem Fahim in Istanbul contributed to this report.