Enviroserv and Wasteman concluded a shareholders’ agreement in 1994 to establish a joint venture company, Vissershok Waste Management Facility (Pty) Ltd, to operate a landfill site. Clause 12 of the agreement provided that Enviroserv would initially manage the business for six months, after which the arrangement would be reviewed. Despite this, Enviroserv continued to manage the business exclusively for more than eight years without objection. In 2003, following changes in Wasteman’s shareholding, disputes arose regarding Enviroserv’s continued exclusive management. The dispute was referred to arbitration. The arbitrator rejected Wasteman’s claims for review or joint management but also rejected Enviroserv’s entitlement to continued exclusive management. Enviroserv appealed to an arbitration appeal tribunal, which upheld Enviroserv’s appeal on the basis that, after the lapse of clause 12, the parties’ conduct gave rise to a tacit agreement allowing Enviroserv to continue rendering services under an open-ended arrangement terminable on reasonable notice. Wasteman successfully applied to the High Court to set aside the appeal award under s 33(1)(b) of the Arbitration Act, alleging that the tribunal committed a gross irregularity by deciding the matter on an unpleaded tacit agreement. Enviroserv then appealed to the Supreme Court of Appeal.