How have the courts treated the liability of a supplier of a roof tile manufacturer in relation to latent defects?

Lord Wilberforce discussed the liability of the supplier of the roof tiles at page 479 as follows: "He thus assumed responsibility for delivering goods 'of merchantable quality'. That means, in this context, goods of the minimum quality to be expected of goods of the description. Is there any reason why this warranty should not be implied against him? To impose upon him liability for latent defects makes him, so far, an insurer in respect of the defects which he could not prevent and of which he did not know. But it is well settled that the implied condition as to fitness extends to latent defects (Randall v. Newson). That this should be so in the case of the manufacturer needs no justification: and where the supplier is a dealer, such as a wholesaler, or retailer, the justification for imposing liability on him is that it is open to him, and is consequently his responsibility, to obtain a similar warranty from his own supplier so that ultimately responsibility can be traced back to where it should lie, that is, with the manufacturer, or whoever else has brought the defect about".