The writ though of right is not of course: i.e. the applicant cannot have it merely for the asking, but must satisfy the High Court that circumstances exist calling for its issue. The procedure regulating the grant and enforcement of the writ is determined by the _Crown Office Rules_, 1906 (rr. 49-68, 125).
_Mandamus_ has always been regarded as an exceptional remedy to supplement the deficiencies of the common law, or defects of justice. Where another legal or equitable remedy exists, equally appropriate, convenient, speedy, beneficial and effectual, the writ will as a rule be refused. It is occasionally granted even when a remedy by indictment is available: but is not issued unless the existence of the duty and refusal to perform it are clearly established, nor where performance in fact has become impossible. The writ is used to compel inferior courts to hear and determine according to law cases within their jurisdiction, e.g. where a county court or justices in petty or quarter sessions refuse to assume a jurisdiction which they possess to deal with a matter brought before them. It has in recent years been employed to compel municipal bodies to discharge their duties as to providing proper sewerage for their districts and to compel anti-vaccinationist guardians of the poor to appoint officers for the execution of the Vaccination Acts; and it is also employed to compel the promoters of railway and similar undertakings to discharge duties imposed upon them towards the public by their special acts, e.g. with reference to highways, &c., affected by their railways or other undertakings. The courts do not prescribe the specific manner in which the duty is to be discharged, but do not stay their hands until substantial compliance is established.
Besides the prerogative common-law writ there are a number of orders, made by the High Court under statutory authority, and described as or as being in the nature of mandamus, e.g. mandamus to proceed to the election of a corporate officer of a municipal corporation (Municipal Corporations Act 1882, s. 225); orders in the nature of mandamus to justices to hear and determine a matter within their jurisdiction, or to state and sign a case under the enactments relating to special cases.