It is common practise, mostly in the business world, for a contract to be entered into by an agent, acting on behalf of someone else, be it a juristic entity or a private person. This well-known principle is called the Law of Agency.
The doctrine of constructive notice applied under the old Companies Act. In terms of this doctrine, and because the constitutional documents of a company were (and still is) in the public domain, outsiders were presumed to have knowledge of any limitations on the powers and capacity of a company and or office bearers.