Two dual UK-Iranian nationals flew home on Wednesday after being released from years of detention in Iran, as the government in London confirmed it had paid a longstanding debt over a cancelled defence contract.

"British Nationals Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori will return from Iran today," British Foreign Secretary Liz Truss said. "They will be reunited with their families and loved ones."

British lawmaker Tulip Siddiq, who represents the district where Zaghari-Ratcliffe's family live in London, also confirmed her constituent's departure from Iran, where she has been detained since 2016.

"It's been 6 long years -- and I can't believe I can FINALLY share this photo," she said on Twitter, posting a picture of a smiling Zaghari-Ratcliffe aboard a plane. 

"Nazanin is now in the air flying away from 6 years of hell in Iran."

Truss confirmed that after months of negotiations, and diplomatic assistance from Oman, London and Tehran had "in parallel" resolved a £394-million ($515-million, 470-million-euro) debt dating back to the 1970s and the era of the Shah of Iran.

The families of both Zaghari-Ratcliffe and Ashoori believe they were being held as political prisoners until the issue was settled.

"The IMS (International Military Services) debt has been settled in full compliance with UK and international sanctions and all legal obligations," Truss said. 

"These funds will be ring-fenced solely for the purchase of humanitarian goods."

Further details on the settlement are set to remain confidential.

The UK has consciously avoided saying the detention of the pair, and others held in Iran, was linked to the debt for an order of tanks that was cancelled after the 1979 Islamic revolution.

Truss has blamed sanctions on Iran for delaying the repayment.

UK-bound

Zaghari-Ratcliffe, a project manager for the Thomson Reuters Foundation, the philanthropic arm of the news and data agency, was arrested in Tehran on a visit to family in 2016.

The mother-of-one, from north London, was sentenced to five years in prison for plotting to overthrow the government. 

Last year she was given a further 12-month jail term for taking part in a rally outside the Iranian embassy in London in 2009.

Ashoori, a retired engineer from southeast London, was arrested in 2017 and jailed for 10 years on charges of spying for Israel. 

A picture shows a family photograph of Anoosheh Ashoori (L) and wife Sherry Izadi (R). Photo: AFP

Both have strenuously denied the charges, while Ashoori in January began a hunger strike at Tehran's notorious Evin prison.

Hopes were raised about Zaghari-Ratcliffe's release after she had her British passport returned to her on Tuesday while a UK negotiating team was in Iran.

It is understood the pair will travel to Britain via Oman, landing back in the UK late Wednesday.

Truss also announced that Morad Tahbaz, an Iranian-American who also holds British nationality, has been released from prison "on furlough" to his Tehran home.  

He was arrested alongside other environmentalists in January 2018 and sentenced to 10 years in jail for "conspiring with America".

"We will continue to work to secure Morad's departure from Iran," Truss added.

'Trumped-up charges'

Sacha Deshmukh, Amnesty International UK's chief executive, welcomed the "fantastic news" of the releases, saying both were "jailed on trumped-up national security charges".

"The government needs to follow up on Nazanin and Anoosheh's release by immediately renewing its calls for the release of the UK nationals Mehran Raoof and Morad Tahbaz, both of whom are still going through an ordeal all too similar to Nazanin and Anoosheh's," he added.

Raoof, a labour rights activist, was detained in October 2020 and was being held in solitary confinement, according to Amnesty.

Dual nationals from Austria, Canada, France, Germany, Sweden and the United States have also been arrested in similar circumstances.

Zaghari-Ratcliffe's husband Richard Ratcliffe staged a hunger strike outside the foreign ministry in London last October after his wife lost her latest appeal, and as government ministers held talks with Iranian counterparts.

Richard Ratcliffe (L), husband of Nazanin Zaghari-Ratcliffe, a British-Iranian held in Iran since 2016, poses for pictures with their daughter Gabriella (R) in his arms after the announcement of his wife release. Photo: AFP

She was freed from prison with an electronic tag in March 2020 because of the coronavirus pandemic but had been held in Iran under a form of house arrest ever since.

Campaigners and families of those held have said that the issue of detainees is being forgotten by the West as powers meet in Vienna to seek to negotiate a revival of the 2015 deal on the Iranian nuclear programme.