A 22-year-old man who was also arrested on suspicion of murder is undergoing treatment for injuries sustained before his arrest.
He remains under police guard in hospital.
A 49-year-old woman held suspected of murder was this week freed on police bail and is due to return to Woking Police Station on August 29.
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Nazanin Zaghari-Ratcliffe's five-year jail sentence is confirmed despite her husband's campaign to bring her home.