“25. It very often happens in professional negligence cases that a defendant will give evidence to a judge which constitutes the reason why he considers that his conduct did not fall below the standard of care reasonably to be expected of him. He may do this by reference to the professional literature that was reasonably available to him as a busy practitioner or be reference to reasonable limits of his professional experience; or he may seek to rebut, as one professional man against another, the criticisms made of him by the claimant’s expert(s). Such evidence is common, and it is certainly admissible… 26. Of course a defendant’s evidence on matters of this kind may lack the objectivity to be accorded to the evidence of an independent expert, but this consideration goes to the cogency of the evidence, not to its admissibility…” 671. As a matter of practice in the TCC, technical and expert opinions are frequently expressed by factual witnesses in the course of their narrative evidence without objection being taken. Such opinion evidence does not have the same standing as the evidence of independent experts who are called pursuant toCPR rule 35 . However, such evidence is usually valuable and it often leads to considerable saving of costs. 672. Having regard to the guidance of the Court of Appeal and the established practice in TCC cases, I conclude that in construction litigation an engineer who is giving factual evidence may also proffer (a) statements of opinion which are reasonably related to the facts within his knowledge and (b) relevant comments based upon his own experience. For example, an engineer after describing the foundation system which he designed may (and in practice frequently does) go on to explain why he believes that this was appropriate to the known ground conditions. Or an engineer brought in by a claimant to design remedial works (which are subsequently challenged as excessive) may refer to his experience of rectifying comparable building failures in the past….” “25. It very often happens in professional negligence cases that a defendant will give evidence to a judge which constitutes the reason why he considers that his conduct did not fall below the standard of care reasonably to be expected of him. He may do this by reference to the professional literature that was reasonably available to him as a busy practitioner or be reference to reasonable limits of his professional experience; or he may seek to rebut, as one professional man against another, the criticisms made of him by the claimant’s expert(s). Such evidence is common, and it is certainly admissible… 26. Of course a defendant’s evidence on matters of this kind may lack the objectivity to be accorded to the evidence of an independent expert, but this consideration goes to the cogency of the evidence, not to its admissibility…”