Joe Biden is taking risks with detainee swap, but US can now test the waters with Tehran on its nuclear programme

US and Iran expected to complete $6bn prisoner swap deal

US-Iran prisoner swap: the detainees due to be freed

Soon after her release, Nazanin Zaghari-Ratcliffe remarked that freedom for a former Iranian political prisoner is never complete since those freed always recall those left behind.

But when five Americans released from Iranian captivity touch down in Qatar on their way back to their families, the mood will be simple, joyous and emotional. By contrast, the drawn out diplomacy that has led to this moment has been the polar opposite – complex, fraught and calculating.