It should be remembered that an invention which at first sight appears obvious might in fact involve an inventive step. Once a new idea has been formulated, it can often be shown theoretically how it might be arrived at, starting from something known, by a series of apparently easy steps. Examiners should be wary of ex post facto analysis of this kind. When combining documents cited in the search report, they should always bear in mind that the documents produced in the search have, of necessity, been obtained with foreknowledge of what matter constitutes the alleged invention. In all cases they should attempt to visualise the overall state of the art confronting the skilled person before the applicant's contribution, and should seek to make a "real-life" assessment of this and other relevant factors. They should take into account all that is known concerning the background of the invention and give fair weight to relevant arguments or evidence submitted by the applicant, without the benefit of hindsight.[GL/ISPE 13.15; ]