“Between those two extremes there are bound to lie much more debatable cases to which, according to their particular circumstances, the Industrial Tribunals are required to apply their expertise in determining whether the border line has been crossed between a resignation that is truly voluntary and a retirement unwillingly made in response to a threat. I doubt myself whether, given the infinite variety of circumstance, there can be much scope for assistance from authority in discharging that task: indeed attempts to draw analogies from other cases may provide more confusion than guidance. In cases where precedent is nevertheless thought to be of value, the authority that will no doubt continue to be cited is Sheffield v Oxford Controls Co Ltd[1979] ICR 396 .”