Nazanin Zaghari-Ratcliffe is a “hostage” in Iran and was on the brink of being freed from jail in Iran almost two-and-a-half years ago until a planned deal collapsed, according to a new documentary.

The mother-of-one’s husband Richard Ratcliffe said the family had even been given a date of December 28 2017 for his wife’s return to the UK.

It is unclear why the deal fell through.

The revelations were made during a BBC Panorama investigation into the detention of British and other western citizens in Iran, which airs on Monday night on BBC One at 7.30pm.

It has long been claimed Mrs Zaghari-Ratcliffe is being held in order to force the UK into settling a multi-million pound dispute with Iran.

The debt dates back to the 1970s when the then-Shah of Iran paid the UK £400 million for 1,500 chieftain tanks.

When he was toppled in 1979, Britain refused to deliver the tanks to the new Islamic Republic but kept the cash, despite British courts accepting that the money should be repaid.

Panorama said that according to its sources, the Ministry of Defence has objected to the repayment.

Mrs Zaghari-Ratcliffe has said the Iranian authorities have told her that her release hinges on the money being returned.

But publicly the Iranian authorities have denied any link between the debt and Mrs Zaghari-Ratcliffe’s imprisonment.

The UK Foreign Office also said they do not “recognise any linkage” between the debt and her imprisonment, adding “it is unhelpful to suggest otherwise”.

Mrs Zaghari-Ratcliffe has so far served four years in prison and is currently on temporary release under effective house arrest at her parents’ home in Tehran due to the Covid-19 pandemic.

It is unclear whether she will be permanently freed or recalled to prison.

She was arrested at Tehran airport in April 2016 as she was returning to London with her daughter, following a visit to her parents to introduce them to their grandchild.

Mrs Zaghari-Ratcliffe was convicted of spying and jailed for five years.

She has been afforded diplomatic protection by the UK Government, which states that she is innocent and that her treatment by Iran failed to meet obligations under international law.

Mr Ratcliffe believes his wife is being held as “diplomatic leverage” by Iran.

The US authorities agree.

US Special Representative to Iran, Brian Hook, told Panorama Mrs Zaghari-Ratcliffe and other western detainees are effectively hostages.

“The Americans that are held in Iran are wrongfully detained and Iran has unfortunately a sad history going back to 1979 of hostage taking, when they took our American diplomats hostage,” he said.

“This is a practice. It’s a tool of statecraft.

“It’s part of Iran’s foreign policy to take people hostage who are innocent and then trade them later for some objective that they think advances their own objectives.”

Iranian Supreme Leader Ayatollah Ali Khamenei said on Sunday war was unlikely but called on Iran’s armed forces to boost their defence capacities, according to his official website, as the country faces increased tension with the United States.

On Saturday, Iran announced plans to boost its ballistic and cruise missile capacity and acquire modern fighter planes and submarines to boost its defences following the U.S. pullout from Tehran’s nuclear agreement with world powers.

“Ayatollah Khamenei emphasised that based on political calculations there is no likelihood of a military war but added that the armed forces must be vigilant … and raise their personnel and equipment capacities,” the website quoted Khamenei as telling commanders of Iran’s air defence forces.

“The Supreme Leader said … the air defence units were a very sensitive part of the armed forces and on the front line of confronting the enemy, and emphasized the need to increase their readiness and capabilities,” the website said in its report on the gathering, which was held to mark Iran’s Air Defence Day.

Saturday’s news of the military development plans came a day after Iran dismissed a French call for negotiations on Tehran’s future nuclear plans, its ballistic missile arsenal and its role in wars in Syria and Yemen.

Iranian President Hassan Rouhani said last month the Islamic Republic’s military prowess was what deterred Washington from attacking it.

Separately, a senior Iranian diplomat met visiting UK Junior Foreign Minister Alistair Burt and urged swift European action on a planned package of economic measures to offset the U.S. pullout from the accord and the reimpositions of sanctions by Washington, the state news agency IRNA reported.

“The imposition of (U.S.) sanctions and pressures and the lack of rapid action by Europe to fulfil their commitments will have serious consequences,” Kamal Kharrazi, a former foreign minister who heads a top foreign policy council, told Burt, IRNA reported.

Iranian officials have said they would decide whether to quit the 2015 nuclear deal with world powers after studying the European package of economic measures that could help offset U.S. sanctions.

“European countries have not been able yet to take necessary measures to secure Iran’s interests under the nuclear agreement,” Kharrazi said.

“(Burt) said Britain’s position is different from that of the United States and we are looking for a European mechanism to make the nuclear accord successful,” IRNA reported.

In a meeting with senior parliamentarian Heshmatollah Falahatpisheh, Burt referred to the case of a British-Iranian dual national detained in Iran, IRNA reported.

“I thank Iran for its humanitarian act to grant Nazanin Zaghari furlough and her meeting with her family, and we hope that this approach will continue until the release and the pardon of such people,” Burt said, according to IRNA.

Britain is seeking the release of Nazanin Zaghari-Ratcliffe, a project manager with the Thomson Reuters Foundation. She was arrested in April 2016 at Tehran airport as she was heading back to Britain with her daughter, now aged four, after a family visit. She was released for three days last month.

Burt, on the first visit by a British minister since U.S. President Donald Trump withdrew from the nuclear deal, earlier met Iranian Deputy Foreign Minister Abbas Araghchi.

Iranian Foreign Minister Mohammad Javad Zarif said on Saturday the talks with Burt had involved “access to banking resources and the sale of oil”.

Iran has been seeking commitment from European signatories of the nuclear deal that it will be able to access the Western banking system and continue to sell oil despite U.S. sanctions.

In a statement before his visit, Burt said: “As long as Iran meets its commitments under the deal, we remain committed to it as we believe it is the best way to ensure a safe, secure future for the region.”

Saudi Arabia has agreed to admit an Iranian diplomat to head an office representing Iranian interests in the kingdom, the official Iranian news agency IRNA reported on Sunday, in a rare move after the rivals broke off relations in 2016.

“An informed diplomatic source said Sunday that Saudi Arabia had agreed to grant a visa to the head … of Iran’s interests section,” IRNA reported. “Observers saw this … as a positive diplomatic step in Tehran-Riyadh relations.”

The office is expected to be set up within the Swiss diplomatic mission in Saudi Arabia, based on an agreement signed in 2017.

There was no immediate official Saudi reaction to the Iranian report.

The kingdom, the regional rival of mostly Shi’ite Iran, presents itself as the guardian of Islamic orthodoxy and custodian of its holiest places in Mecca and Medina.

Riyadh severed diplomatic relations after Iranian protesters stormed the Saudi Embassy in Tehran following the execution of a Shi’ite cleric in Saudi Arabia in January 2016.

Both countries agreed to Switzerland’s offer of its traditional policy of good offices and to act as a diplomatic channel between the two countries.

Saudi Arabia welcomed President Donald Trump’s decision in May to withdraw the United States from an international nuclear agreement with Iran and to reimpose economic sanctions on Tehran.

In an interview published on the Iranian Foreign Ministry’s website, the ministry spokesman said there had been a “breakthrough” in relations between the two regional rivals.

“Up until two weeks ago, no visa had been issued for the names that we had submitted a long time ago,” spokesman Bahram Qasemi said.

“But within the last week or two, there has been a breakthrough and I think there are indications that the office for the protection of interests will be opened,” he added.

Tension between the two countries have surged in recent years, with Saudi Arabia and Iran supporting opposite sides in wars in Syria and Yemen and rival political parties in Iraq and Lebanon.

 Anti-government protests broke out in Iran for the third day running on Saturday (December 30) as separate state-sponsored rallies were staged to mark the end of unrest that shook the country in 2009, according to Iranian news agencies and state media.

Social media postings showed protests in the capital’s streets, including crowds gathered outside Tehran University and dumpsters set on fire.

Openly political protests are rare in the Islamic Republic, where security services are omnipresent but there is considerable discontent over high unemployment, inflation and alleged graft.

Some of the new protests have turned political over issues including Iran’s costly involvement in regional conflicts such as those in Syria and Iraq.