Through no fault of its own, this is a very American-centric view of early computing. I'm pretty sure that at the time this was written, the story of COLOSSUS was still highly classified by the British government. It has since been declassified, and you might read about it in this book [1].
Colossus was an important machine, but I don't think it was a stored-program computer (it was programmed through a plug-board.) On the other hand, Wikipedia's entry on stored-program computers says "In 1936 Konrad Zuse anticipated in two patent applications that machine instructions could be stored in the same storage used for data", though I don't think it was implemented in any of his machines.
Isn't the concept kind of implicit in a universal Turing machine?
1: https://www.amazon.com/dp/0199578141