Nazanin Zaghari-Ratcliffe was almost freed by Iran three years ago but the deal collapsed... weeks after Boris Johnson tried to intervene in her case, new documentary claims 
Jailed mother Nazanin Zaghari-Ratcliffe was due to be released on December 28, 2017, before deal with Iran collapsed. The exact reason for the failure of the deal is not known.
https://www.dailymail.co.uk/news/article-8656795/Nazanin-Zaghari-Ratcliffe-freed-Iran-three-years-ago-deal-collapsed.html