Serious irregularity: error in computation

In Ducat Maritime Ltd v Lavender Shipmanagement Inc [2022] EWHC 766 (Comm) the arbitrator by error added to the sum claimed in arbitration the amount of an unsuccessful counterclaim, giving rise to a sum greater than the amount sought. Although the sum awarded was reduced to the amount of the claim, the respondent sought to overturn the award for serious irregularity. The question for Butcher J was whether a clear error of this sort, not admitted by the arbitrator at the time, constituted serious irregularity.

The facts