Abstract
The Mental Capacity Act 2005 provides the legal framework governing what practitioners can do, and when, where it is believed someone's capacity to make decisions is compromised by a disturbance in the functioning of the mind or the brain. In 2012 the Court of Appeal in the case of DL v A Local Authority identified a lacuna in that no legal regime existed to intervene in situations where a person did not lack capacity under the Mental Capacity Act 2005, but was being abused, coerced, or otherwise unduly influenced in their decision‐making. The Court of Appeal held that the inherent jurisdiction of the High Court could be used to fill this gap. Since 2012, applications made under this ‘rediscovered’ inherent jurisdiction have increased apace. Through an analysis of subsequent case law, this article argues that there are three areas of concern and confusion in the way the jurisdiction has developed since 2012: when it should apply, what it should do, and on what basis judges decide what it should do. This has resulted in incoherent, inconsistent, and unprincipled developments, which are fundamentally at odds with the primary aims of the common law.