2. The question whether the provisions of an agreement impose a penalty must, however, be determined as a matter of substance rather than of mere form (see, e.g., Clydebank Engineering and Shipbuilding Co. Ltd. v. Castaneda [1904] UKHL 3; (1905) AC 6, at p 9; Dunlop Pneumatic Tyre Company Ltd. v. New Garage and Motor Company Ltd. [1914] UKHL 1; (1915) AC 79, at pp 86-87, 92; Campbell Discount Co. Ltd. v. Bridge (1962) AC 600, at p 624). If, as a matter of substance, the provisions of an agreement operate, in the case of breach or non- performance, to impose some additional or different financial obligation in the nature of a punishment (as distinct from a genuine pre-estimate of damage or withdrawal of a mere incentive), they will prima facie impose a penalty (cf., e.g., Clydebank Engineering, at pp.15,19; Dunlop, at pp 86ff., 97, 100-101; Legione v. Hateley [1983] HCA 11; (1983) 152 CLR 406, at p 445).