One of seven people arrested in a Metropolitan Police counter-terrorism operation has been released without charge.
The 30-year-old woman had been arrested in west London on Thursday.
Six other people are still being held in custody.
Police say the operation is not linked to the Olympics or Paralympics.
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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.
The victim was travelling between Seven Sisters and Highbury and Islington when she was assaulted.