Upon Mutual Written Agreement
In United Bank Ltd v. ASIF (not notified on 11 February 2000), it was found that a contract with an anti-oral amendment clause (“… No variation. valid or effective, unless it can be effective by one or more written acts signed by the parties… ) only by a written document in accordance with this clause. The trial court`s decision, which was approved by the Court of Appeal in the event of a refusal of appeal (in the context of a guarantee decision, although not qualified as a relevant consideration), was that no oral amendment of the written provisions could have any legal value. In this case, it was also found that the person who would have obtained the oral amendment to the contract was not entitled to do so. The starting point of the party invoking the clause was that it meant that any amendments had to be made in writing and signed by both parties and that it was not open to the parties to amend the agreement orally. The purpose of the clause is to promote safety and avoid false or reckless assertions of an oral agreement. Such clauses may also prevent a person from a large organization from establishing a document that, unknowingly and unintentionally, is incompatible with a contract to which the organization is involved, and thus sets a threshold of proof. The three judges of the Court of Appeal have spoken on this issue.
The general meaning is that the judges were hesitant not to give effect to the clause, but that they could not, in principle, find a fundamental basis for limiting the nature or form in which an agreement could be amended. That is why perhaps everyone has reluctantly agreed that agreements containing such clauses can nevertheless be amended by oral agreement or behaviour, although Lord Justice Underhill, in particular, has stressed that such clauses are not possible to have no value. He stated: “In many cases, parties considering relying on informal communication and/or conduct to change their obligations under a formally agreed contract will face difficulties in demonstrating that both parties intended to change their legal relationships in what has been said or done; and there may be authority problems. These difficulties can be much greater if they have accepted a provision that requires a formal amendment. The Court preferred World Online`s decision and found that a contract that in principle contains a clause that any change can be made in writing may be different by oral agreement or conduct. We often see treaties with terms such as: “This agreement must not be amended, except by the mutual written agreement of the contracting parties.” The recent decision of the Court of Appeal in Globe Motors Inc. e.a. against TRW Lucas Varity Electric Steering Ltd. e.a.  EWCA Civ 396 took into account the effects of similar clauses containing a clause, the “comprehensive agreement,” Amendment: This agreement, which contains the attached annexes, is the only agreement between the parties with respect to the purpose of this agreement.
It can only be amended by a written document (i) which explicitly refers to the provision to amend this agreement and (ii) is signed by both parties.” The same judge, who sat before the Court of Appeal in World Online Telecom Ltd/I-Way Ltd  EWCA Civ 413 case (and apparently did not know of his early decision at United Bank), found, however, that the question of whether the parties could repeal a clause in a written agreement was the unwritten modification of the contract (in this case “… this agreement is not applicable unless it has been established in writing and signed and signed by both parties” so that it is capable of making the effect of a summary conclusion.