Iran’s ambassador to the UK has claimed that talks are under way between the two countries over a £400m debt cited as an obstacle to the release of British dual nationals held by the regime. Hamid Baeidinejad told an Iranian newspaper that there was change in attitude in the government of Boris Johnson to resolve the decades-long dispute over the non-delivery of tanks and arms following the 1979 revolution. “Finalising the payment method requires a mutual agreement,” the envoy told Etemad newspaper. “Talks are under way to determine the details of how the agreements will be implemented.” The families of at least two British dual nationals, Anoosheh Ashoori and Nazanin Zaghari-Ratcliffe, say that resolution of the debt is critical to securing their eventual release. Anoosheh Ashoori, 65, was arrested in 2017 during a visit to Tehran to see his mother and jailed for 12 years after the Iranian authorities accused him of spying for Mossad. His son told the National last year that the best hope for his release was “not the Iranian judicial system, it’s the debts that the UK has to pay Iran”. Richard Ratcliffe, the husband of Nazanin, has also pressed UK officials to resolve the dispute. The long-running dispute centres on a 1971 contract for more than 1,700 tanks and armoured vehicles that was aborted after the Shah was deposed. Britain accepts that it owes money to Iran but says that it could not pay the bill because of European Union sanctions imposed on Iran’s defence ministry in 2008. The two sides were embroiled in court cases that had not settled the final amount before sanctions were imposed, the London court has heard. A hearing, scheduled for last week, was postponed. The UK government has reportedly been looking at ways of paying the money via humanitarian aid to try avoid breaking the sanctions regime. The UK government did not immediately comment on the ambassador’s comments. Britain’s International Military Services paid £382 million into a court-controlled account in 2002 until the dispute was settled, which has risen to more than £500 million with interest. Iran has applied for a special sanctions’ waiver from Britain’s sanctions’ authority that would allow the money to be paid to its central bank, but no decision has been made.