(and their legal advisers) that, in cases involving an alleged breach of a contractual duty, throwing every available resource and the kitchen sink into an expert report will more often detract from the report than add to it. An expert’s evidence will be more credible, and realistic, if they first ask themselves which resources the party who is alleged to have breached the duty would reasonably have been expected to use, bearing in mind the nature of the duty. Although it is important to be thorough, excessive industry might give the impression that the expert will go to any lengths to reach the ‘right’ answer for their client. Applying the Wrong Test The test that Mr V should have been applying was: what would a reasonably competent monitoring surveyor have done in the circumstances? Instead, Mr V fell into the common trap of explaining what he would have done in the circumstances, line-by-line, and figure-by-figure. His evidence was that was what he did, so that is what Watts should have done too. The problem with this analysis was that there were no margins of error. He ignored the broader parameters against which a monitoring surveyor’s performance should have been judged, if the correct test had been applied. So, for example, he neglected to mention the plus or minus 10% metric habitually used in negligent valuation cases. Where the duty is one of reasonableness, an expert must take care to undertake their exercise from the position of a reasonable party, giving a range of reasonable results. A failure to do so will lead a judge to conclude that the expert has applied the wrong test, greatly reducing the value of their evidence. Attempt to Mislead More seriously, Coulson J found that Mr V had misled the court. As mentioned above, Mr V had conducted his own detailed analysis of the costs of development, rather than simply check the calculations of the developer. He justified this approach by referring to guidance published by the Royal Institution of Chartered Surveyors, which he quoted as saying: “the Project Monitor … may have to develop his or her own elemental breakdown of construction costs