Research on Prevalence of Rape in UK Prisons needed

Article here. Excerpt:

'Sex happens in prison. Some prisoners will have consensual sexual relationships with others whilst they serve their time. Others may be sexually assaulted by prisoners or by prison staff. Some may report the abuse to staff but others will stay silent.
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The Howard League for Penal Reform established the Commission on Sex in Prison in 2013 and conducted the first ever review of consensual and coercive sex inside prison in England and Wales. Over the past two years the Commission heard evidence from the Chief Inspector of Prisons, the Prisons and Probation Ombudsman, prison governors, researchers, health professionals, prisoners and their partners.
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Identifying and combating sexual abuse inside prison should be a priority. A study of former prisoners in 2004 found 1 per cent had been raped and 5 per cent had been victims of coerced sex. Her Majesty’s Inspectorate of prisons found that 1 per cent of prisoners who completed an anonymous survey during inspections reported they had been sexually assaulted. The small percentages mask the true extent of the problem. There are on average 85,000 people in prison in England and Wales. More than 165,000 people are received into prison annually. It is possible that between 850 and 1650 prisoners could be victims of sexual assault while inside. The number of sexual assaults could be higher as evidence indicates that some victims are assaulted several or many times.'