This is because it is a recognized principle of law that a contract will rarely be totally illegal or void: certain parts may be entirely lawful in themselves, while others are valid. Where the illegal or void parts can be “severed” from the rest of the contract on the well-known principles of severance such will be done and the rest of the contract enforced without the void part. It is permissible for courts to adopt this course where the objectionable part of the contract involves merely a void step or promise and is not fundamental, and it is possible to simply strike down the offending part without re-writing or remaking the contract for the parties and without altering the scope and intention of the agreement; and lastly, the contract, shorn of the offending parts, retains the characteristics of a valid contract. See on these Vol. 9 Hals. Laws of England (4th Edn.) p.297 in paragraph 430. See also Commercial Plastics Ltd. v. Vincent (1964) 3 All E.R. 546, C.A.
— Nnaemeka-Agu, JSC. Adesanya v Otuewu (1993) – SC.217/1989