Eight men have been arrested on suspicion of raping a young teenage girl, after dawn raids at several addresses in East London and Hertfordshire.
Five 23-year-olds, two 24-year-olds and one 21-year-old are being held in custody at a police station.
Officers from the Met's Sapphire Command are investigating alleged offences that took place between May and November 2012.
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The prison was originally opened in 1852 as a mixed prison before becoming the first female-only local prison in England in 1902.