This case establishes important principles regarding exception procedure in South African civil procedure and the distinction between cancellation and variation of contracts containing non-variation clauses. It reinforces that: (1) upholding an exception disposes of the pleading, not the action, and leave to amend should ordinarily be granted; (2) the excipient bears the burden of showing that on every reasonable interpretation the plea discloses no defence; (3) tacit agreements can terminate contracts notwithstanding non-variation clauses; and (4) for contracts giving rise to continuing obligations, tacit cancellation operating in futurum (terminating future obligations while preserving past accrued obligations) constitutes cancellation, not variation, and does not offend non-variation clauses. The case provides guidance on when matters should be determined on exception versus at trial, particularly where contextual evidence may be necessary.