I remember when the floating "Coastels" which had been used as military accommadation at RAF Stanley in the Falkland Islands were offered as prison ships once MPA was ready. They too were turned down because the accommodation was substandard for the poor little convicted thugs who got a £10 pound call home phone card at Christmas when serving personnel were only given £5. It appears that the only other difference between a PC and murder is that your pension doesn't get cut in half when you only serve half your term for murder.