The husband of U.K. charity worker Nazanin Zaghari-Ratcliffe, who has been detained for more than five years in Iran, has gone on a hunger strike again after a court decided she has to spend another year in prison.

Richard Ratcliffe launched the effort on Sunday outside the British government’s Foreign Office in central London.

He plans to maintain a “constant vigil” by sleeping in a tent outside the building’s main entrance in an effort to pressure Prime Minister Boris Johnson to secure the release of his wife and other detained dual British-Iranian nationals, Amnesty International said.

Zaghari-Ratcliffe served five years