When disruption hits, the market starts hunting for the right certificate. Under English law and in GAFTA arbitration, there is no magical document. What matters is contemporaneous evidence and its connection to performance of the actual contract.
A chamber certificate or similar official paper may help, but it does not decide the case. Arbitrators make that decision themselves. A letter sent by an agent on the day of the event may carry more weight than a polished certificate obtained a month later.
The working file should include correspondence with agents, terminals, brokers and owners, port authority instructions, Notices to Mariners, AIS records, and communications with the counterparty. The point is not volume for its own sake, but whether the file shows prevention rather than mere commercial inconvenience.
Form matters less than provenance. Who wrote the document, when it was created, and whether the author actually knew the facts will usually matter more than whether it came on letterhead.
Common mistakes are backfilling documents, mixing legal advice with factual evidence, and building the case around cost and difficulty rather than impossibility of performance. Each document should help answer one question: why this contract could not be performed.
Notice comes first. The evidence file and chronology come next. Arbitration comes later. The evidence is being created now.