How now should the respondent have pleaded the invalidity of the transaction? In considering whether the invalidity of the transaction was pleaded, I must bear in mind the fact that pleadings are no longer required to be technical in formulation. Subject to the requirement that parties must not offend against any of the known rules of pleadings as laid down by law, such as that they should not plead evidence or omit to plead facts which, when proved, may result in surprise to the other side, or facts which are frivolous or vexatious, or which may tend to prejudice, embarrass or delay the trial of the action, all that a pleader is now required to do in such a case is, where necessary, to allege illegality or invalidity and plead facts from which inferences of law thereof could be drawn: see on this Knowles v. Roberts (1888) 38 Ch.D. 263, at p.270 to 271; Willis v. Lovick (1901) 2 K.B. 195. That is the proper rule. But the court will itself take notice of the illegality or invalidity of a contract on which a party is relying if it appears on the face of the contract or from the facts pleaded, although the party has not expressly averred that it is illegal or invalid: see Windhill Local Board v. Vint (1890) 45 Ch.D 357; Gedge v. Royal Exchange Assurance (1900) 2 Q.B. 214.
— Nnaemeka-Agu, JSC. Adesanya v Otuewu (1993) – SC.217/1989