The prime minister's affirmation of rehabilitation as a guiding principle of penal policy is welcome (Editorial, 23 October), his vision of how it is to be achieved less so. In some respects he appears to be repeating the same ideas that have contributed to the relentless rise in the prison population with limited reduction in reconviction rates. A research study we have undertaken in co-operation with the Jersey probation service has found a strong link between probation officer skills and the reconviction of those people they supervise in the community: put simply, the higher the level of skill, the lower the level of reconviction. One of the lessons is that successful rehabilitation is dependent on, among other things, sufficient investment in the training and education of the professionals involved. Without an investment in the required resources, the prime minister's rhetoric will remain just that. It's now time to move towards a more serious commitment to developing evidence-based policies. Professor Maurice Vanstone, Professor Peter Raynor, Dr Pamela Ugwudike Swansea University

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