This case involves a dispute between a Norwegian oil and gas company (the claimant) and a US-based commodities trading group (the defendant) over *demurrage fees* related to the sale of propane gas. The key issues revolve around *contractual interpretation, **unilateral mistake, and whether a **second settlement agreement* existed to correct an earlier mistake. Below is a detailed explanation of the facts, issues, and the court’s decision:

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### *Facts*###

1. *Contract for Sale of Propane Gas*:
   - The parties entered into a contract for the sale of propane gas.
   - The contract included provisions for *demurrage*, which is a fee payable if a ship is not loaded or unloaded within the agreed time.

2. *Dispute Over Demurrage*:
   - The claimant sued the defendant for the balance of demurrage owed.
   - The defendant argued that the contract required demurrage claims to be made within *90 days*, and if not, the claim would be forfeited.

3. *First Settlement Agreement*:
   - The parties’ representatives reached an agreement on the amount of demurrage owed (the *first settlement agreement*).
   - However, the claimant’s representative made a *mistake in the calculations*, resulting in an understated demurrage amount.
   - The defendant’s representative realized the mistake but chose not to inform the claimant.

4. *Second Settlement Agreement*:
   - The claimant argued that during a later phone call, the parties agreed to correct the mistake (the *second settlement agreement*).
   - The defendant denied that any such agreement was made.

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### *Issues*###

1. *Time-Bar Clause*:
   - Did the contract invalidate demurrage claims made after 90 days?

2. *Unilateral Mistake*:
   - Was the first settlement agreement void due to the claimant’s unilateral mistake in calculating the demurrage amount?

3. *Equitable Doctrine of Mistake*:
   - Does an equitable doctrine of mistake apply to these facts, allowing the agreement to be voided?

4. *Second Settlement Agreement*:
   - Did the parties make a second agreement to correct the mistake in the demurrage amount?

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### *Court’s Decision*###

1. *Time-Bar Clause*:
   - The High Court held that the final version of the contract *did not contain a time-bar clause* requiring demurrage claims to be made within 90 days. Therefore, the claimant’s claim was not invalidated by delay.

2. *Unilateral Mistake*:
   - The court ruled that the *first settlement agreement was not void for mistake. The claimant’s mistake was not about a **term of the contract* but rather about a *background fact* (the calculation of demurrage). At common law, a unilateral mistake only applies if the mistake relates to a *contractual term*, not a background fact.

3. *Equitable Doctrine of Mistake*:
   - The court rejected the existence of an *equitable doctrine of mistake* in this context. Aikens J confirmed that the decision in *Great Peace Shipping Ltd v Tsavliris Salvage International Ltd [2003]* had already rejected the idea of an equitable defence of mistake for cases where a party is mistaken about a fundamental assumption underlying the contract.

4. *Second Settlement Agreement*:
   - The court found that the *second settlement agreement* did exist. During the phone call, the parties agreed to correct the mistake in the demurrage amount. As a result, the claimant was entitled to claim the *full demurrage amount*.

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### *Key Legal Principles*###

1. *Unilateral Mistake at Common Law*:
   - A contract can be void for unilateral mistake only if:
     - The mistake relates to a *term of the contract* (not a background fact).
     - The other party knew or ought to have known about the mistake.
   - In this case, the claimant’s mistake was about a *calculation error*, not a contractual term, so the agreement was not void.

2. *Equitable Doctrine of Mistake*:
   - The court reaffirmed that there is no separate equitable doctrine of mistake for cases where a party is mistaken about a fundamental assumption underlying the contract. This principle was established in *Great Peace Shipping Ltd v Tsavliris Salvage International Ltd [2003]*.

3. *Formation of Subsequent Agreements*:
   - Parties can modify or correct a contract through a subsequent agreement, even if the original agreement contained a mistake. The court found that the *second settlement agreement* effectively corrected the mistake in the demurrage amount.

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### *Significance of the Case*###

- *Clarity on Unilateral Mistake*:
  - The case clarifies that unilateral mistake at common law applies only to mistakes about *contractual terms*, not background facts or calculations.
- *Rejection of Equitable Mistake*:
  - The court’s rejection of an equitable doctrine of mistake reinforces the principle that equitable remedies are not available for mistakes about fundamental assumptions.
- *Importance of Clear Contract Terms*:
  - The case highlights the importance of ensuring that contracts clearly state terms, such as time-bar clauses, to avoid disputes.

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