Strachey was also the lead programmer behind the programming language CPL, the great-grandfather of C (via BCPL and B). CPL was too ambitious and was never completely implemented - it tried to do everything; a bit like Perl 6 really.
The overview paper:http://comjnl.oxfordjournals.org/cgi/content/abstract/6/2/134 is quite interesting; sadly it is now behind a pay-wall. There are some features of the language, such as type inference, which have not become common until recently. It also has some obvious poor decisions with hindsight - the same character starts and ends blocks; all lower case letters are single-character variable names; multiple-character variable names must be capitalised (this is done to allow implicit multiplication, ie, xyz=x*y*z). I suspect it could be implemented without huge difficulty with modern tools. Unfortunately, the full definition was never published, and only exists in a few copies of 'The CPL Working papers' archived in university libraries. Perhaps one day google will scan it.
The first sign of maturity is the discovery that the volume knob also turns to the left.