“We make the following general comments on the duty to give reasons. (1) The duty is a function of due process, and therefore of justice. Its rationale has two principal aspects. The first is that fairness surely requires that the parties especially the losing party should be left in no doubt why they have won or lost. This is especially so since without reasons the losing party will not know (as was said in Ex parte Dave ) whether the court has misdirected itself, and thus whether he may have an available appeal on the substance of the case. The second is that a requirement to give reasons concentrates the mind; if it is fulfilled, the resulting decision is much more likely to be soundly based on the evidence than if it is not. (2) The first of these aspects implies that want of reasons may be a good self-standing ground of appeal. Where because no reasons are given it is impossible to tell whether the judge has gone wrong on the law or the facts, the losing party would be altogether deprived of his chance of an appeal unless the court entertains an appeal based on the lack of reasons itself. (3) The extent of the duty, or rather the reach of what is required to fulfil it, depends on the subject matter. Where there is a straightforward factual dispute whose resolution depends simply on which witness is telling the truth about events which he claims to recall, it is likely to be enough for the judge (having no doubt summarised the evidence) to indicate simply that he believes X rather than Y; indeed there may be nothing else to say. But where the dispute involves something in the nature of an intellectual exchange, with reasons and analysis advanced on either side, the judge must enter into the issues canvassed before him and explain why he prefers one case over the other. This is likely to apply particularly in litigation where as here there is disputed expert evidence; but it is not necessarily limited to such cases. (4) This is not to suggest that there is one rule for cases concerning the witnesses’ truthfulness or recall of events, and another for cases where the issue depends on reasoning or analysis (with experts or otherwise). The rule is the same: the judge must explain why he has reached his decision. The question is always, what is required of the judge to do so; and that will differ from case to case. Transparency should be the watchword.” 21. As was put by Lord Phillips MR (as he then was) in English v Emery Reimbold & Strick Ltd[2002] 1 WLR 2409 : “We would put the matter at its simplest by saying that justice will not be done if it is not apparent to the parties why one has won and the other has lost”
“The reasons for a decision must be intelligible and they must be adequate. They must enable the reader to understand why the matter was decided as it was and what conclusions were reached on the “principal important controversial issues”, disclosing how any issue of law or fact was resolved. Reasons can be briefly stated, the degree of particularity required depending entirely on the nature of the issues falling for decision. The reasoning must not give rise to a substantial doubt as to whether the decision-maker erred in law, for example by misunderstanding some relevant policy or some other important matter or by failing to reach a rational decision on relevant grounds. But such adverse inference will not readily be drawn. The reasons need refer only to the main issues in the dispute, not to every material consideration. Decision letters must be read in a straightforward manner, recognising that they are addressed to parties well aware of the issues involved and the arguments advanced…”