No one at Hanslope, seeing the strange civilian boffin cycling across with a handkerchief around his nose (it was his hay fever period) could have connected him with the success of the assault on Normandy.
And by now his part in the necessary conditions for making it was something that lay in the past; the success he wanted was of something truly and more wholly his own.
As ten years before, it was his privilege to continue in his own way, with the least waste of energy, the civilisation which demanded harsher sacrifice from others.
And it was another kind of invasion that he had in mind, one not yet ready for announcement.
The successful passage of 6 June 1944 roughly coincided with the point at which it became possible for Alan and Don Bayley to get down to work on constructing the Delilah equipment, clearing up the rather messy efforts that the Prof had made on his own.
The main task was that of building the circuit to produce the highly accurate 'orthogonal' response.
It was the design of this circuit that had absorbed most of Alan's earlier thought and experiment.
He had realised that it could be synthesised out of standard components.
This was an entirely new idea to Don Bayley, as was the mathematics of Fourier theory that had been used to attack it.
It was a tough problem, which Alan said had involved spending a whole month in working out the roots of a seventh degree equation.
Although he was an amateur and self-taught electronic engineer, he was able to tell his new assistant a good deal about the mathematics of circuit design, and for that matter was by now able to show most of them in the laboratory hut a thing or two about electronics.
But it needed Don to bring his practical experience to bear on the problem, and to tame the straggly bird's nest.
He also kept beautifully neat notes of their experiments, and generally kept Alan in order.