Update: Morad Tahbaz on hunger strike
A British-US national released from Evin Prison in Iran only to find himself back in custody two days later was on Sunday taken from the notorious jail to a hotel in Tehran.
Wildlife conservationist Morad Tahbaz, 66, who also holds Iranian citizenship, was first allowed out on the same day last week that charity worker Nazanin Zaghari-Ratcliffe and retired civil engineer Anoosheh Ashoori were released and then allowed to return to Britain.
A Foreign Commonwealth and Development Office spokesman confirmed that Mr Tahbaz was now in a hotel in the capital.
"We have been in touch with Morad's family throughout the day and continue to lobby the Iranian authorities at the highest levels to allow him to return home immediately, as the Iranian government committed to doing," the spokesman said.
Britain said it secured his furlough, along with the release and return of the two other dual nationals.
This came after the UK finally agreed to settle a £400 million ($526.7m) debt from the 1970s, which fuelled tension between the countries for decades.
Mr Tahbaz, who has cancer, was arrested during a crackdown on environmental activists in January 2018.
He is a prominent conservationist and board member of the Persian Wildlife Heritage Foundation, which protects endangered species.
Mr Tahbaz was sentenced to 10 years in prison with his colleagues on vague charges of spying for the US and undermining Iran's security.
The UK and the US are working closely with each other to try to secure his permanent release.
Family members hoped that Mr Tahbaz, who was born in Hammersmith, west London, would be freed under the deal under which Mr Ashoori and Ms Zaghari-Ratcliffe arrived back in the UK early on Thursday.
It is not clear if Mr Tahbaz has been fitted with an ankle tag by the Iranians, which the UK foreign office had been told was set to happen.
"We continue to work night and day to secure the release of our wrongfully detained citizens, including US-UK citizen Morad Tahbaz," a US State Department spokesman said.
"Simply put: Iran is unjustly detaining innocent Americans and others and should release them immediately."
