P, a manager and union member, took part in a go-slow and then strike as part of industrial action. The employer said that any employee who was not prepared to keep to their contract in full would be sent home without pay. P refused to sign an undertaking saying that from now on (i.e. after the strikes of the previous days) she was prepared to perform her contractual obligations fully and so was sent home without pay. She sued D, arguing that she had been willing to work and so the employer owed her pay. CA dismissed her claim, holding that she had withdrawn her goodwill.
Ralph Gibson: an employment contract for a manager contained an implied term/duty to serve the employer faithfully, which she had breached. Since she was only willing to offer partial performance (working but without goodwill/serving her employer faithfully) the employer was entitled to refuse and bring the contract to an end.