This section is from the book "Uncle Alberts Manual Of Practical Photography And Guide To The Reproductive Processes", by Powell Perry. Also available from Amazon: Uncle Alberts Manual Of Practical Photography And Guide To The Reproductive Processes.
This remarkable invention which has done so much to facilitate the gathering of in camera evidence first came into the news of the world when the late Lord Justice Bunkum naively enquired "... Why were the defendants enclosed in "a bottle at the time?"(laughter in court). The prosecuting counsel then explained that the unusual shape was caused by the keyhole through which the series of photographs had been taken. Before showing a selection of such photographs - extracted from the series that resulted in a conviction in the famous Entwhistle v. Arsenal case - I propose to give a brief description of the ingenious apparatus of which I happen to be the modest inventor.
A cardboard notice which reads "Quiet, Please "..._"Men at Work "... "Out of Order "... or, indeed, anything else you like, is securely attached to the back of an ordinary Box-Type Camera. The camera is then loaded in the normal way and attached to the door by means of two or three of my patent whilst if it does not contain any of the above figures the best position for the hole can be determined by studying a Moorhen in its natural surroundings or a Purple Patched Wood Louse hiding in a stamp album.
Gripwell Suction Pads (4 6 per box of twelve assorted sizes, obtainable from any reputable ironmonger or chemist), so that the Lens Aperture coincided with the keyhole. Next, the doorknob is quietly unscrewed and replaced with a gilded india-rubber bulb (for working the camera shutter, presumably - Ed.). Finally, and unless an existing hole made by the hotel staff for private reconnaissance can be located and utilised, a Viewing Hole must be bored through the door. This need not be very obtrusive - 1/2 inch diameter is usually quite sufficient - and we suggest that the room number can often be used to provide local camouflage; e.g., if the number contains 6, 8, 9 or 0 the hole should be bored thus. . . .
When fixed as described, the Keyhole Camera is ready for instant use; in fact immediate use is advisable since too much loitering about corridors is apt to look suspicious. Simply peep through the Viewing Hole, wait for the dickey and press what everyone else thinks is the door knob. The following series of keyhole Studies present many interesting features, some of which are touched on in different sections of this book. Unfortunately many features are touched on in impossible to touch on anywhere else, but which were clearly presented in the original series, were missing from the collection when we got it back from the mounters.