My Humber does not have a visible key code so I went to my local locksmith, AADaves Broadway and Emerson in Mpls where he felt the pins, cut a key and then made a second. I don't remember the cost but very reasonable. Had to have been well under $20 or I would remember the cost.
Now that I knew the lock worked I contacted this person on eBay WILMOT BREEDEN KEY NGN50 VINTAGE BICYCLE BIKE of RALEIGH INDUSTRY ENGLAND NOS, he was not able to match s photo of my key to his masters so I ordered two blanks and had my local locksmith cut those based on the key he made.
I liked the Wilmot Breeden blank as it is the NOS blank that Raleigh used for these steads. An ALL STEEL bicycle should have a steel key, it is what a gentleman would do.
The seller lives in the former shadow of the Nottingham factory and that is in keeping with stories true or otherwise.