Boris Johnson “spoke frankly” with his Iranian counterpart during a two-hour meeting in Tehran, the Foreign Office has said.
During what his department described as “two hours of frank talks”, the UK’s Foreign Secretary expressed his “grave concerns” over jailed British-Iranian woman Nazanin Zaghari-Ratcliffe.
Mr Johnson is also expected to meet Iranian president Hassan Rouhani on Sunday.
He began Saturday’s talks by expressing his condolences for a powerful earthquake which killed more than 400 people in November.
Speaking to the Iranian foreign minister Mohammed Javad Zarif, Mr Johnson also expressed the UK’s continued support for the nuclear deal.
Donald Trump has previously criticised the deal as “one of the worst and most one-sided” agreements the US has ever signed, and was in turn criticised for moving against it.
Sky’s Diplomatic Editor, Dominic Waghorn, noted that the Iranian foreign ministry issued a short statement saying that the two sides discussed “various matters including economic, banking and trade relations”.
“It was quite a long meeting, and it was followed by a meeting with the speaker of the Parliament and other Iranian officials,” Waghorn said.
“It was a pre-planned visit, so there were lots of issues that were being discussed, but obviously very close to Boris Johnson’s heart – and important to his career – is the plight of Nazanin Zaghari-Ratcliffe, after the mistake he made in front of MPs.”
According to the Foreign Office, Mr Johnson and Mr Zarif “spoke frankly about the obstacles in the relationship” between the two nations.
It is the first trip of a British Foreign Secretary to Iran since 2015 and only the third since 2003, and comes as Mr Johnson continues a three-day tour of Oman, Iran and the United Arab Emirates.
The Foreign Office said the pair discussed “the consular cases of British-Iranian dual nationals” although the department did not name Mrs Zaghari-Ratcliffe specifically.
Mrs Zaghari-Ratcliffe is serving a five-year sentence for allegedly planning to overthrow the Iranian government – a claim she and her family have always denied.
She was arrested in April 2016 at Tehran airport after visiting her relatives with her daughter.
Mrs Zaghari-Ratcliffe has always stressed that the trip was a holiday, but she was jailed for sedition after authorities linked her to mass protests in 2009.
Dominic Waghorn noted that the Foreign Secretary was meeting those on the moderate side of the Iranian government – but in the background you have the hardliners, who may want to keep dual nationals in prison because it deters other foreigners from going to the country pursuing their own interests.
“Tomorrow, Mrs Zaghari-Ratcliffe is back in court for a scheduled hearing where she may have her sentenced increased. If she does, that will be embarrassing for the Foreign Secretary to have gone there without securing any progress – in fact the reverse, if that happens – and of course it will be devastating for her family.”
Mrs Zaghari-Ratcliffe’s husband Richard told Sky News it was encouraging that Mr Johnson had constructive and frank discussions and good news that he was meeting the president.
He said: “I’m really pleased that he met with foreign minister Zarif, that it lasted for a couple of hours and that it was both frank and constructive. I think in our case a frank discussion and a constructive one can only be a good thing.”
He said Mr Johnson also met others who might be able to help with her case. “I was hoping to go on this trip… and he said he would check if the Iranian authorities thought it was a good idea. In short he felt that I could have gone for a couple of days but it would be more helpful and more likely for her to come home if he went on his own and was able to press that case amongst a range of issues.”
The Foreign Office said: “Overall, it was a useful meeting at the start of the Foreign Secretary’s visit to Iran.
“The Foreign Secretary subsequently met the Speaker of the Iranian Parliament, Mr Ali Larijani, and the Secretary of the Supreme National Security Council, Mr Ali Shamkhani,” the department added.
The Government is considering repaying around £400m from a pre-1979 arms deal, but both sides say it is not to do with Mrs Zaghari-Ratcliffe.
However, the US made a similar payment as Iran released four of its citizens in 2016.