In Rock Advertising Limited (respondent) v MWB Business Exchange Centres Limited (complainant)  UKSC 24, the Supreme Court delivered its judgment in an area described as a « fundamental issue of contract law ». Lord Sumption, who delivered the main judgment, completely resolved any uncertainty by stating that « the law should and makes a contractual provision requiring the request of certain formalities for an amendment ». When a court declares a contract void, it means that the contract has no force or effect, so that neither party is bound to it and neither party can avail themselves of it. As a general rule, this is because the acceptance of an offer constitutes the « agreement » – not the contract – between the parties. Statements of intent, mood or policy that are unclear, that the courts can act safely, cannot have legal effect. Lord Sumption concluded that there was no contradiction between a general rule allowing the informal conclusion of contracts and a specific rule under which amendments to an existing treaty had to be made in writing, and referred to legal systems such as the Vienna Convention on Contracts for the International Sale of Goods (1980) and the UNIDROIT Principles for International Trade Agreements. 4. Edition (2016), which also do not set formal requirements for the validity of a commercial contract, while ensueing NOM clauses.