R v Monopolies and Mergers Commission, ex parte South Yorkshire Transport Ltd [1993] 1 WLR 23

A proposed acquisition between bus operators prompted an investigation by the Monopolies and Mergers Commission. Its statutory jurisdiction depended partly on the geographical reach of the businesses: the area had to qualify as a substantial part of the country under the Fair Trading Act 1973. A bus company sought judicial review, disputing whether that condition was satisfied. The challenge required the courts to examine both the meaning of the statutory threshold and the Commission's assessment of the area concerned. The House of Lords therefore had to distinguish defining the legal test from deciding how it applied to the evidence.

Whether the Commission misunderstood “a substantial part of the United Kingdom”, and how closely courts should review its evaluative application of that statutory jurisdictional threshold.

The House of Lords allowed the Commission's appeal and upheld its jurisdictional assessment. The statutory expression required interpretation by the court, but its application involved evaluation rather than a simple numerical boundary. The Commission's reasoning had to be read as a whole. Although an understanding equating substantial merely with non-trivial would have been problematic, the complete report demonstrated a fuller assessment of the area's importance and characteristics. The Commission had not radically misconstrued the statutory standard. The court therefore did not substitute its own evaluation. The judgment preserved judicial control over the legal meaning while recognising an area of permissible judgement in applying that meaning to the facts.

Courts determine the meaning of a statutory standard, but an evaluative expression may leave the authorised body a range of lawful applications. Judicial review can correct a radical misconstruction without substituting the court’s preferred assessment within that range.

South Yorkshire Transport demonstrates why identifying a statutory phrase as a legal question does not always produce a single mechanically correct application. Courts determine its meaning, but broad evaluative language can leave an authorised decision-maker a range of lawful assessments. The case is valuable beside Khawaja and Puhlhofer because it prevents an oversimplified division between law and fact. It does not permit an agency to invent its jurisdiction: a radical misunderstanding of the statutory threshold would still justify intervention.