Documents circulated by government departments on behalf of ministers, setting out policies, principles, and practices for the exercise of ministerial powers delegated to public officials. In some instances circulars provide mere administrative guidelines and have no legal effect. However, where circulars give effect to statutory requirements (e.g. circulars providing guidance to local planning authorities under the Town and Country Planning Act 1990) they will have legal effect. In such cases circulars are subject to judicial review. Whether or not a particular circular has legal effect depends on the interpretation of the legislation in terms of which it was issued (Patchett v Leathem  65 TLR; Gillick v West Norfolk and Wisbech Area Health Authority  1 AC 112 (HL).