Leighton Contractors v Western Australian Government Railways Commission

Leighton Contractors Pty Ltd (Leighton) and the Western Australian Government Railways Commission (Westrail) were parties to a contract for the construction of a railway line. A dispute arose between them concerning the interpretation of certain clauses within the contract, specifically relating to the payment for work performed by Leighton. The matter came before the High Court of Australia.

The central legal issue before the High Court was the proper construction of the contract, particularly concerning whether Leighton was entitled to be paid for certain work performed in excess of the original scope of the contract, and if so, on what basis. This involved an examination of the contractual provisions governing variations and the calculation of payment for such variations.

The High Court considered the express terms of the contract and the surrounding circumstances to ascertain the parties' intentions. The Court analysed the provisions relating to the measurement and valuation of work, and the mechanism for payment for work that deviated from the original plan. The principles of contractual interpretation, focusing on the plain meaning of the words used and the overall context of the agreement, were applied to resolve the dispute. The Court ultimately determined the extent of Westrail's liability to Leighton under the contract.