Over the last two decades increasing attention has been paid to the rights and safety of the subjects of clinical research. A key safeguard against any abuse has been the requirement to obtain the subject's informed, valid or true consent, which has been defined by the Medical Research Council as ‘consent freely given with proper understanding of the nature and consequences of what is proposed’ (M.R.C., 1962–3). However, it has been recognized by the M.R.C. that it may not be possible to obtain such consent from, among others, some subjects who are mentally ill. Whether or not a research project should be carried out on such subjects should depend, they say, on whether or not ‘there are reasonable grounds for believing that a particular new procedure will contribute to the benefit of that particular patient…’, and further, ‘when true consent cannot be obtained, procedures which are of no direct benefit and which might carry a risk of harm to the subject should not be undertaken’ (M.R.C., 1962–3).