Before I introduce Elmer, the first of Grey’s tortoises, a little background on Grey’s technical skills. We already learnt from the previous post that Grey was building "wireless" sets with his Dad in 1919. The BNI Archives have a photo of a young Grey Walter at a metal turning lathe, so he appears to be quite a practical person. 
Grey was building electronic equipment, and at least one of them was patented. [a note on patent searching: my early patent searching was largely a slow and arduous process using cumbersome techniques. Recently Google has made it much easier to search for patents, albeit U.S. registered ones. So there may be other Grey Walter patents around, but one of them was also filed in the U.S. where this one came from.] In the U.K. Grey Walter’s patent application for the Wave-Form Analyzing Apparatus is : August 6, 1947, Serial No. 766,707 . It is searchable and found here in the U.S. Patent office August 11, 1953, Serial No. 2,648,822 .