The Ministry of Justice says there will be an investigation.
Nicholas Casley was 59 and from Mullion in Cornwall.
He'd appeared at Truro Crown Court last week, where he pleaded guilty to a total of 14 charges - including 2 for having sex with a child.
He was due to be sentenced today (Thursday 19th July)
The Justice Secretary David Gauke is currently involved with improvements at the troubled prison, after an Inspector raised serious concerns about a number of issues - including self harm and suicide.
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