The Iranians are holding three more Britons as well as Nazanin Zaghari-Ratcliffe amid claims of a vendetta against Theresa May, it emerged today.

Tehran is said to have been left furious when the Prime Minister detained and deported two of its officials when she was Home Secretary in 2013.

Today it emerged that up to four dual British-Iranian nationals are in jail there, including Mrs Zaghari-Ratcliffe who was imprisoned last year.

Another Briton in the notorious Evin jail near the capital is grandfather Kamal Foroughi, 78, who was also arrested for alleged espionage six years ago.

The oil and gas worker was jailed in 2013 for eight years but it only came to light two years ago when his family spoke out.

His son Kamran said: ‘My dad has always strenuously maintained his innocence and we believe him. We are not aware of any evidence that justifies the espionage charge’.

He told the Guardian: ‘My daughters have lived half their lives without seeing Grandpa and keep asking when he is coming home. All I can do is give them a hug’.

Mr Foroughi holds dual British-Iranian citizenship and said he was working for Malaysian energy giant Petronas, working with officials in Tehran and offering scholarships to students.

It is not clear what led to his arrest but he was given seven years in prison for spying and an extra year for having alcohol in his home.

Human rights experts have said that Iran’s police and secret services are very suspicious of dual nationals, especially if they are British or American.

The UN has said this has increased since 2015 when Barack Obama struck a nuclear deal, which President Trump now says they are violating.

Whitehall sources have also told The Sun that Theresa May upset Tehran when she was Home Secretary and detained two Iranian officials when they landed at Heathrow even though they had visas.

They were placed in an immigration detention centre and deported within a week.

Boris Johnson said today everything is being done to free jailed British mother Nazanin Zaghari-Ratcliffe from prison in Iran.

In Dublin for talks with his Irish counterpart, the Foreign Secretary briefly responded to the question as he entered the meeting.

When asked what he would do for Mrs Zaghari-Ratcliffe, Mr Johnson said: ‘No stone unturned.’

The Foreign Secretary is set to discuss paying a £400million ‘debt’ to Iran within weeks amid claims the decades-old dispute is being settled hastily to help free a jailed British mother.

The long-running controversy over the money will be raised when the Foreign Secretary visits the country next month, say Whitehall sources.

There are fears that Nazanin Zaghari-Ratcliffe, 38, is being held as a ‘bargaining chip’ in the dispute.

It dates back to a 1970s arms deal, when the Shah of Iran ordered and paid for 1,750 Chieftain tanks and support vehicles from a firm owned by the Ministry of Defence.

But the deal was halted after the Shah was deposed in 1979, and Britain kept the money.

An international court ordered the UK to reimburse Tehran, but international sanctions mean Britain has so far been unable to return the money, which is being held by the High Court.

Now Mr Johnson and Chancellor Philip Hammond are said to have authorised Government lawyers and officials to work a way around the UN sanctions in order to settle the ‘debt’.

According to reports, Iranian regime hardliners have said they expect the deal to be settled as part of a list of demands before freeing Mrs Zaghari-Ratcliffe, who has been held in Tehran since April 2016.

Source » dailymail