Immigration Act powers to detain are not time limited. However, domestic and European Court of Human Rights (ECHR) case law provides that detention must last for no longer than is reasonably necessary for the purpose for which it is authorised and must not be of excessive duration.
Under the terms of Rule 34 of the Detention Centre Rules 2001 (No. 238) Immigration Service removal centres must ensure that arrangements are in place for detainees to have a physical and mental examination by the medical practitioner within 24 hours of their arrival. The purpose of this is to identify any immediate and significant mental or physical health needs. Rule 35(5) requires medical practitioners to pay particular attention to any detainee whose mental condition appears to require it and to make arrangements for their care.