Evidence also emerged that suggests some of the country's most dangerous convicted criminals are switching from taking cannabis to heroin in an attempt to beat drug tests. In one month more than half the positive drug tests were for heroin.
The revelations follow the publication today of the findings of an unannounced short inspection last September of Belmarsh high-security jail, in south- east London, by the Chief Inspector of Prisons, Sir David Ramsbotham.
He will hold an inquiry later this year to review the visiting arrangements for prisoners deemed to be an exceptional risk at the country's six high- security jails.
Sir David's report highlights the condition faced by the inmates kept in the separate special security unit inside Belmarsh.
All prisoners within the unit, which holds up to 48 men, including convicted IRA terrorists such as Paul "Dingus" Magee, who is serving 25 years for murdering a special constable, have closed visits - a plastic screen divides inmates from prisoners. "For some this may mean they can go for years without being able to touch their children or wife, with the obvious effects on relationships," noted the report.
Sir David said there was far too little out-of-cell activity for Category A prisoners. They are only allowed out for 90 minutes a day.
There are six exceptional-risk inmates at Belmarsh, most of whom are IRA members, and 27 men considered high-risk.
The Inspectorate is concerned that at some high-security jails contact is allowed and wants to ensure prisons get the right balance between the needs of security and humanity.
In February, the Tory government turned down a recommendation by the former Chief Medical Officer, Sir Donald Acheson, that closed visits at the SSUs should be ended. But the Prison Service did agree to regular three-monthly health checks for inmates.
Results from mandatory drug tests at Belmarsh reveal an alarming increase in the number of inmates found to have taken heroin. The proportion rose from 9 per cent of the positive results in December 1995 to a maximum of 54.5 per cent in June last year.
The inspectors also came across a mystery during their visit: how 12,000 prison library books had gone missing since 1991.Reuse content