The children of Anoosheh Ashoori have said their first conversation with their father after he returns home from Iran will be an “extraordinary” moment when “our suffering is going to end”.

Dual national Mr Ashoori, 68, a retired civil engineer, was arrested in August 2017 while visiting his elderly mother in Tehran, and held in Evin prison.

During his time in detention, he was subjected to torture and a catalogue of inhumane experiences, according to Amnesty International UK.

The husband and father is set to be reunited with his family after being released on Wednesday and boarding a flight out of Iran along with Nazanin Zaghari-Ratcliffe, another British-Iranian.

Mr Ashoori’s daughter Elika, 35, told the PA news agency the news had been “very, very sudden” and the family were “over the moon” after five years of turmoil.

Speaking alongside her brother Aryan, 32, she said: “The hardest part would be when he tried to take his own life.

“He wanted to remove himself from the equation, in part because they were threatening us, our safety. They were telling him they were monitoring our movement.

“Him trying to take his own life was, in a sense, a way to protect us. I think that’s as dark as this story got.”

The siblings said they would need to “tread carefully” because of the trauma their father had suffered, but they hoped his homecoming would mark a return to normality.

Elika, a pastry chef, has made a cake to greet him with when he steps off the plane.

“We’re over the moon. We have exercised cautious optimism for a while now but we’re happy we are finally able to let go,” she said.

“I had planned to make an elaborate cake for him but because this was very, very sudden I only had time to make a small cake.”

Aryan said: “If he’s back tonight, this will be the first time he’s sleeping in a room without 15 other men. It will just be his wife.”

Elika added: “When he comes back here our suffering is going to end. No suffering is worse than what we’ve experienced.

“We will face certain new challenges due to the fact that there has been a trauma and we have to tread carefully and take his feelings into consideration and our feelings into consideration.

“It’s a fragile scenario so we need to be careful with how we go forward.”

After Mr Ashoori arrives back in the UK, the siblings plan to spend the first night together with him and their mother Sherry Izadi, his wife, as a family.

“I think we’re going to treat the moment without any preconceived notion of what we should do,” said Aryan, a music company director.

“In many ways it will feel like any conversation we’ve had with him in the past, but in other ways it will be extremely extraordinary.”

Aryan said the family had learned of a potential change to Mr Ashoori’s circumstances, but after so much false hope they had remained cautious.

“We were aware that some movements were happening but it was unclear whether something would really happen or not. There has been times where there has been false hope.

“Even today, when they were at the airport in Iran, there were people saying they had already left, which wasn’t true.

“Until he landed abroad we didn’t know for sure that it was actually happening. Obviously him getting on the plane is significantly closer.”

Despite living in the UK for 20 years, Mr Ashoori was convicted of spying for Israel’s Mossad intelligence agency and sentenced to prison for 10 years.

In January 2020, his wife, who lives in London, said she feared he had no “hope in hell” of being released.

Aryan warned that despite the family’s relief at Mr Ashoori’s return, the problem of other dual nationals being held in detention remained.

“I feel like a major battle has been won but the war is far from over in terms of justice,” he said.