Psychiatrists have long recognised that routine clinical practice needs to be shaped and informed by external evidence (Lewis, 1958). Psychiatric researchers were among the first to utilise multi-centre randomised controlled trials (demonstrating the effectiveness of antipsychotics), and psychologists were among the first in the health field to develop techniques of meta-analysis. Social workers, too, point to their tradition with the publication of one of the earliest controlled trials (Lehrman, 1949).