In Our Time 's Ada Lovelace program, by necessity, involved quite a bit of discussion of Charles Babbage. Babbage, with some help from Lovelace, imagined a good portion of the computing machine that Turing and others would later build.
Melvyn's guests felt that there wasn't a direct connection between Babbage (1830) and Turing (1945), that Babbage's contributions were essentially lost to science.
This seems a bit odd, as the Wikipedia article on Babbage mentions that his son created six difference engines. To this I can add an additional note from my library. I have a copy of the 1911 Encyclopedia Britannica (11th ed), which includes an article on Babbage and one on Calculating Machines. I've scanned all of the former and portions of the latter (PDF 8MB ). (See also the "love to know" 1911 project , but their article doesn't match my copy. Microsoft apparently republished the encyclopedia in 1995.)
Briefly, the article on Babbage focuses on his mathematical pursuits, including an essay deploring the decline of science in 19th century England (some things never change). The article describes both the Difference and Analytic engines much as we understand them now, though it misses the significance of the programming design. The article on Calculating Machines praises the Difference Engine as a real device with well understood principles, but states that the Analytical Engine did not progress beyond sketches. It does, however, refer interested readers to a comprehensive book by Babbage's son.
I'm left with the impression that Melvyn's guests understated the extent to which portions of Babbage's work survived into the 20th century.
 OS X Black and White PDFs are vastly larger than Adobe's B&W PDFs.