Relatives of the 30 dual nationals jailed by Iran's Revolutionary Guards since 2016 appealed for their release on Wednesday, a plea for international help coinciding with the week-long Commonwealth heads of Government Meeting across London.
"I don't want him to die in prison and the Canadian government are are only hope," said Maryam Malekpour, the sister of Saeed Malekpour, a Canadian-Iranian web developer arrested in Iran in 2008 and charged with agitation against the regime and insulting the sanctity of Islam. Mr Malekpour is serving a life sentence.
Ms Malekpour made her plea at a parliamentary meeting in Westminster as Canadian Prime Minister Justin prepared to sit down with Prime Minister Theresa May, just steps away in Downing Street.
He is one of dozens of leaders who have descended on the capital for The Commonwealth of Nations, an intergovernmental organisation of 53 member states mostly former territories of the British Empire
Human rights groups hope the international event will also draw attention to the plight of political prisoners in Iran.
Vida Mehrannia, the wife of Swedish-Iranian academic Dr Ahmedreza Jalali, told journalists that she still can't bring herself to tell her six-year-old son that his father was arrested in April 2016. Dr Jalali has staged two hunger strikes and his health is failing. He was invited to speak at a scientific workshop but was arrested and, in February 2017, sentenced to death by the Iranian Revolutionary Courts on charges of espionage.
Ms Mehrannia said she has no idea why her husband was imprisoned: "He is completely innocent."
Labour MP Graham Jones said the situation faced by the prisoners and their families is appalling.
“These two men have been jailed by the Iranian regime on fabricated charges of trying to undermine the Islamic Republic. They are only two of many people who have been physically and mentally tortured in jails cells in Iran in order to extract false confession,” Mr Jones said in opening the meeting in Parliament on Wednesday.
There has been a sharp rise in the arrest of dual nationals since 2015, when an international nuclear deal raised hopes of detente with the West. Since then, however, there has been rising tensions with Britain, Germany and France who are pushing for tougher sanctions against Iran.
Prior to 2105, the number of dual nationals detained at one time was in single figures. Of the 30 arrested since 2016, 19 have European citizenship, human rights campaigners said.
Richard Ratcliffe, the husband of a British charity worker held in Iran for more than two years, called on Theresa May in early April to intervene in her case after Foreign Minister Boris Johnson failed to secure her release.
Mrs Zaghari-Ratcliffe was arrested at Tehran airport on April 3, 2016 and jailed for five years for sedition. She had denied the charges and dismissed claims that she was seeking to overthrow the government through her work with the philanthropic arm of the Thomson Reuters media group.
Mr Ratcliffe has described the period as a "dark two years."
The UK Foreign Office on Wednesday said the government would continue to approach each case "in a way that we judge is most likely to secure the outcome we all want. Therefore we will not be providing a running commentary on every twist and turn."
Mr Ratcliffe has said that he believed the main stumbling block remained an unpaid £400 million bill over an aborted arms deal for Britain to supply tanks and armoured vehicles to the regime of the Shah of Iran. The deal was was scrapped following the 1979 revolution.
Campaigners are now focusing on the fourth birthday of the couple’s daughter Gabrielle, which falls in June, as a potential release date.