Luke Van Sickle, president of the prison guards' union at Lucasville, said the shadow of the riot is always present at the 1, 625-acre prison, where 1, 365 inmates are housed.

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Shadow justice secretary Sadiq Khan told MPs that the current prison population - which has reached a new high - was about "3, 000" higher than when Mr Clarke took office.

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Once a potent symbol of American frustration with the Vietnam War, the prison is now a tourist attraction, in the shadow of an upscale high-rise building owned by a Singapore businessman.

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Meanwhile, shadow justice secretary Dominic Grieve said the money would have been "better spent on prison overcrowding and monitoring criminals released into the community".

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For Labour, Shadow Justice Secretary Sadiq Khan claimed the government was "cutting too far and too fast" in the prison and probation services.

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