“As I have already said, the plea of estoppel in the Defence was worded in an ambiguous way, and at best it is in the discretion of this Court whether to allow the appellant to raise a point which was pleaded but deliberately omitted from argument in the Court below: Hickman v. Kent or Romney Marsh Sheepbreeders Associaton (1920) 3 T.L.R. 163. If the respondent had objected to the points being raised we should have had to consider whether there was any reason why it should be allowed to be raised for the first time here. However, since no objection was made and the point was in fact argued, it may be well to deal with it.”