Nazanin Zaghari-Ratcliffe has announced she is again beginning a hunger strike – this time joined by husband Richard even as they remain thousands of miles apart.
The West Hampstead woman has now been in jail in Iran for 1,169 days.
According to Richard, she called family to let them know she was striking again, after a three-day strike in January.
Richard said: "Today I received a phone call from Nazanin in prison. She had informed the judiciary that she has begun a new hunger strike (she will drink water) - to protest at her continuing unfair imprisonment.
"This is something she had been threatening for a while. Nazanin had vowed that if we passed Gabriella's fifth birthday with her still inside, then she would do something - to mark to both governments - that enough is enough. "This really has gone on too long."
The couple's daughter Gabriella turned five earlier this week.
Richard said that, as in January he had vowed not to let Nazanin go through another hunger strike alone, he would also not eat.
He will also stand vigil outside of the Iranian embassy in Knightsbridge.
Richard has demanded three things - Nazanin's immediate release, for there to be an immediate visit to Nazanin by the British Embassy to check on her health, and if no release is granted to her in the next few weeks, a visa for him to go to Iran.
Nazanin herself has only one demand: unconditional release.
Kate Allen, Amnesty International UK's director, said: "This is a truly heartbreaking situation.
"Nazanin has already been through so much, while her tireless husband Richard has strained every sinew to get Nazanin out of jail and back to the UK where she belongs.
"Nazanin is a prisoner of conscience, unfairly jailed after a sham trial and subjected to all manner of torments - including months in solitary conferment and endless game-playing over whether she would receive vital medical care.
"It's shocking that it's come to this, and we and countless people across the county fervently hope the Iranian authorities will now finally do the right thing and release Nazanin."
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