There has been a rapid growth in the number of patients receiving secure and special care in private hospitals, although their overall numbers are still comparatively small. The behavioural modification unit at St Andrews Hospital, Northampton, has the largest concentration of detained patients outside the National Health Service (NHS), but there are plans to increase the number of beds at Kneesworth House, Royston, Herts, and Stockton Hall, Yorkshire. St Andrews Hospital has been run as a charitable trust but Kneesworth House and Stockton Hall are currently owned by a private French company, Generale de Santé division of Generale d'Eau, together with Langton House, Dorset, which provides places for disturbed adolescents. Marks & Thornicroft (1990) noted that recent entrants into the private sector have been from private for profit rather than voluntary non-profit providers, catering for what are seen as “market niches” such as eating disorders, impotence, alcohol or substance abuse, and stress reactions. They criticise these developments, claiming that few people benefit and that the “bull market” in private hospital development challenges the catchment area concept and seems to be producing a two-tier system of psychiatric care in Britain.