Comorbidity of severe mental illness and substance misuse is now common in general psychiatry (Regier et al, 1990), and perhaps almost standard in forensic psychiatry (Snowden, 2001). It is also reflected in child and adolescent psychiatry (Boys et al, 2003) and even in old age psychiatry (Jolley et al, 2004). The range of hazards associated with substance misuse in people with mental illnesses includes elevated risk of relapse of psychosis (Cantwell & Harrison, 1996), increased frequency of hospitalisation (Bartels et al, 1993), poorer compliance with treatment (Jablensky et al, 1992), higher levels of treatment-resistance (Bowers et al, 1990), impairment of the integrity of therapeutic regimes in hospital settings and in hostels in the community (Sandford, 1995), stress in the community (Drake & Wallach, 1989), higher rates of homelessness (Scheller-Gilkey et al, 1999), increased suicidality (Drake & Wallach, 1989), and increased potential for antisocial behaviour and crime of both an acquisitive and a violent nature (Stewart et al, 2000; Sinha & Easton, 1999). The misuse of substances is therefore a significant obstruction to the effective use of psychiatric treatment, and the financial cost associated with such clinical adversity must run into millions of pounds.