In response to pressures on mental health inpatient beds and a perceived 'crisis in acute care', Crisis Resolution Teams (CRTs), acute home treatment services, were implemented nationally in England following the NHS Plan in the year 2000: an unprecedentedly prescriptive policy mandate for three new types of functional community mental health team. We examined the effects of this mandate on implementation of the CRT service model. Two hundred and eighteen CRTs were mapped in England, including services in all 65 mental health administrative regions. Eighty-eight percent (n = 192) of CRT managers in England participated in an online survey. CRT service organization and delivery was highly variable. Nurses were the only professional group employed in all CRT staff teams. Almost no teams adhered fully to government implementation guidance. CRT managers identified several aspects of CRT service delivery as desirable but not routinely provided. A national policy mandate and government guidance and standards have proved insufficient to ensure CRT implementation as planned. Development and testing of resources to support implementation and monitoring of a complex mental health intervention is required.