The plaintiffs, who were railway contractors, undertook to construct a line of railways for the defendants, the Victorian Railways Commissioners. The Engineer-in-Chief had given his final certificate, in which he found that the plaintiffs had been overpaid in an amount of 1,423l., and his decision on this matter under the contract was final. The plaintiffs then proceeded to arbitration, as they were empowered to do under the contract, and submitted a large number of items to the arbitrators, only one of which under the contract was referable. The amount of this referable item was 30,065l. The arbitrators made an award in favour of the plaintiffs, and awarded them the sum of 20,800l., and to their award they added the following words: "freed and exempt from all deductions on account of previous payments, or of any claims for set-off on any other ground whatsoever."