“Where ... a question of law involved is the construction of a "one-off" clause the application of which to the particular facts of the case is an issue in the arbitration, leave should not normally be given unless it is apparent to the judge upon a mere perusal of the reasoned award itself without the benefit of any adversarial argument, that the meaning ascribed to the clause by the arbitrator is obviously wrong. But if on such perusal it appears to the judge that it is possible that argument might persuade him, despite first impression to the contrary, that the arbitrator might be right, he should not grant leave; the parties should be left to accept, for better or for worse, the decision of the tribunal that they had chosen to decide the matter in the first instance." He continued at page 743D: “ … rather less strict criteria are in my view appropriate where questions of construction of contracts in standard terms are concerned. That there should be as high a degree of legal certainty as it is practicable to obtain as to how such terms apply upon the occurrence of events of a kind that it is not unlikely may reproduce themselves in similar transactions between other parties engaged in the same trade, is a public interest that is recognised by the Act ... but leave should not be given even in such a case, unless the judge considered that a strong prima facie case had been made out that the arbitrator had been wrong in his construction; and when the events to which the standard clause fell to be applied in the particular arbitration were themselves "one-off" events, stricter criteria should be applied on the same lines as those that I have suggested as appropriate to "one-off" clauses." Lord Diplock thus explained that for a "one-off" case, it had to be "apparent to the judge on a mere perusal" that "the arbitrator is obviously wrong"; while for a "standard term" case, the test was "rather less strict", but the applicant still had to establish a strong prima facie case “that the arbitrator had been wrong”
"It is at least open to serious doubt that (as was in effect decided by the arbitrator) the parties had agreed to limit the scope of Morris Homes’ obligations to complete the works by reference to "all reasonable endeavours" (by clause 4), and yet had at the same time effectively agreed (by clause 3.1) to require the works to be carried on (and carried on to completion) by endeavours going beyond the "all reasonable endeavours" of clause 4."