‘Undoubtedly. I shall not forget your claim. Meanwhile, is there any other?’ ‘Yes,’ said Sir Charles Bunford placidly, ‘I think my claim to have established an alibi is stronger than any you have heard yet. Birmingham is more than a hundred miles from London. A certain butler in Birmingham would swear that he saw me and spoke to me on a certain afternoon. A photographer in Birmingham would swear that he photographed me on that same afternoon, and would be able to produce the negative. Yet during the whole of that afternoon I was in London, as the evidence of many of my friends would show. And all the evidence would be given in good faith.’ ‘And how was this miracle accomplished?’ the chairman asked. ‘I’ll tell you the story as briefly as I can. I went to stay for a fortnight with an old friend of mine, a bachelor named Fraser, who has a house outside Birmingham. He is a keen ornithologist. He employs in the preparation of specimens and so on a curious character called Mitten, who is just as keen on birds as Fraser himself. Fraser only has Mitten’s spare time. Mitten’s regular work is with a Birmingham photographer, for whom he does developing and also has charge of the stock of negatives. Fraser is quite unlike me in the face, except that we both have the same deficiency of colour in the hair, but we are of about the same height and build. There is also a slight similarity in our voices. That was the rough material that I had at my disposal, and no doubt you can guess how I got my results from it.’ ‘You’d better continue,’ said the chairman, smiling. ‘On the day before I left I pointed out to Fraser that a similarity in mass often prevented a dissimilarity in detail from being noticed, and that the attitude of expectant attention is a frequent source of error. Fraser asked me, as I had thought he would, what I meant and what I was getting at. I replied that by taking advantage of two facts I had mentioned he could probably get himself mistaken for me. He said that nobody would make the mistake. I said that Hammond’s butler would make it on the following afternoon, if he cared to try the experiment. ‘“I’d like to try it, but it’s impossible. That butler has known me for the last two years, and he has only seen you four or five times in the afternoon. How could he be taken in?” ‘“He has always seen you in dark and chastened clothing, such as it is your custom to wear. He has always seen me with a gray bowler, a light suit, white spats, and a distinctive necktie. He expects to see me to-morrow afternoon, because I borrowed an umbrella there to-day, and said I would bring it back then. All you have to do is to wear my clothes, and hand in that umbrella. He will expect to see me. He will actually see my clothes on a man of about my figure. The hall at the Hammonds’ house is rather dark, and you will have the sun behind you. It’s quite certain the man will be mistaken.”