9.11.2017 A & Ors v Secretary of State for the Home Department [2004] EWCA Civ 1123 (11 August 2004) of the person concerned. He is entitled to have regard to precautionary and preventative principles rather than to wait until directly harmful activities have taken place, the individual in the meantime remaining in this country. In doing so he is not merely finding facts but forming an executive judgment or assessment. There must be material on which proportionately and reasonably he can conclude that there is a real possibility of activities harmful to national security but he does not have to be satisfied, nor on appeal to show, that all the material before him is proved, and his conclusion is justified, to a "high civil degree of probability". Establishing a degree of probability does not seem relevant to the reaching of a conclusion on whether there should be a deportation for the public good. 23. Contrary to Mr Kadri's argument this approach is not confusing proof of facts with the exercise of discretion – specific acts must be proved, and an assessment made of the whole picture and then the discretion exercised as to whether there should be a decision to deport and a deportation order made." 34. Lord Hoffmann stated, at paragraph 56: "In any case, I agree with the Court of Appeal that the whole concept of a standard of proof is not particularly helpful in a case such as the present. In a criminal or civil trial in which the issue is whether a given event happened, it is sensible to say that one is sure that it did, or that one thinks it more likely than not that it did. But the question in the present case is not whether a given event happened but the extent of future risk. This depends upon an evaluation of the evidence of the appellant's conduct against a broad range of facts with which they may interact. The question of whether the risk to national security is sufficient to justify the appellant's deportation cannot be answered by taking each allegation seriatim and deciding whether it has been established to some standard of proof. It is a question of evaluation and judgment, in which it is necessary to take into account not only the degree of probability of prejudice to national security but also the importance of the security interests at stake and the serious consequences of deportation for the deportee." 35. Mr Gill submits that the underlying principle to be applied in approaching Section 21(1) is the principle that the Secretary of State must not act in an arbitrary way. There are different levels of suspicion and, in the present context, a high level is required, it is submitted. Substantial investigation is required before a suspicion can be a reasonable suspicion. 36. The Commission accepted, at paragraph 46, that "the extent, nature, independence and reliability of the evidence are relevant. The extent to which obvious lines of enquiry, which could have been followed, have been ignored is relevant…..It is all the circumstances which are relevant". The Commission accepted, at paragraph 48, that the evidence "does have to be scrutinised carefully and its weaknesses and gaps examined to see if it does provide such grounds [the statutory grounds] or whether suspicion exists or survives because of a failure to investigate matters in obvious ways which would have cast a clearer light, one way or the other, on the point." 37. Paragraph 49, the Commission stated: "What weight is attached to any particular piece of evidence is a matter for consideration in any particular case in the light of all the evidence, viewed as a whole and not as isolated pieces. … Whilst the absence of arrest on criminal charges or interview can be an indicator as to the existence of reasonable grounds, it must be remembered both what material is admissible for these purposes and inadmissible or not usable for criminal trial purposes, and the nature of the matters in respect of which reasonable grounds for suspicion or belief has to be shown." 38. At paragraph 51, the Commission stated, http://www.bailii.org/ew/cases/EWCA/Civ/2004/1123.html 10/113