The folders MS. Eng. misc. b. 265/C.104-MS. Eng. misc. b. 265/C.114 were all kept together by Strachey under the general heading 'Numerical Analysis etc. Flutter, Codiagonal Methods', though the material refers more widely to various problems on which he worked 1952-1959; it also continues to c.1961-1962 during his period as a private consultant after leaving the National Research Development Corporation, and especially to his collaborative paper on matrices. The material may have been assembled for the projected book Introduction to Programming.