“We agreed it on the phone”: Rock Advertising and written contract changes
Why a clause requiring signed written changes mattered in Rock Advertising v MWB, and what to collect when an informal payment arrangement is disputed.
A phone call may resolve a practical problem in the moment while leaving the parties with different ideas about the contract. Check how the agreement says changes must be made before treating an informal discussion as the final position.
Jurisdiction discussed: England and Wales. Case: Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24. Judgment date: 16 May 2018.
What happened and what the Court decided
An office occupier sought to rely on an oral agreement changing its payment schedule. The licence required variations to be in writing and signed. The Supreme Court allowed MWB’s appeal: the alleged oral variation did not satisfy that requirement. The majority explained why such formalities can be effective, while recognising that estoppel may sometimes prevent injustice in limited circumstances.
What the decision does not settle
The case did not hold that every contract must be written, or that an email always meets every variation clause. It also did not finally resolve the separate consideration issue. Any estoppel argument requires careful evidence; the informal promise itself is not automatically enough.
Preparing for a consultation
- Locate the original variation clause and check whether later documents altered it.
- Preserve the proposed schedule, emails, messages and any written confirmation of the call.
- List payments and other actions taken afterwards, recording dates and who said what without reconstructing a more favourable version.
Questions to take to a lawyer
- What form of agreement did this clause require, and was that form actually followed?
- Did the person involved have the relevant authority?
- Is there evidence of a distinct representation or reliance that needs separate examination?
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Official sources
Sources checked on 19 October 2026. The press summary assists readers but is not part of the judgment’s reasons. This article is a case-reading note, not advice on an individual matter. Current law, later decisions and any procedural deadlines require separate checking.