"In one sense it is true that, if the application of that approach leads the members of the tribunal to conclude that the dismissal was unfair, they are in effect substituting their judgment for that of the employer. But that process must always be conducted by reference to the objective standards of the hypothetical reasonable employer which are imported by the statutory references to "reasonably or unreasonably" and not by reference to their own subjective views of what they would in fact have done as an employer in the same circumstances. In other words, although the members of the tribunal can substitute their decision for that of the employer, that decision must not be reached by a process of substituting themselves for the employer and forming an opinion of what they would have done had they been the employer, which they were not."
"First of all, there must be established by the employer the fact of that belief; that the employer did believe it. Secondly, that the employer had in his mind reasonable grounds upon which to sustain that belief. And thirdly, we think, that the employer, at the stage at which he formed that belief on those grounds, at any rate at the final stage at which he formed that belief on those grounds, had carried out as much investigation into the matter as was reasonable in all the circumstances of the case. It is the employer who manages to discharge the onus of demonstrating those three matters, we think, who must not be examined further."