Starting a new thread for this piece of news.....
https://www.narniaweb.com/2025/08/tom-bonington-cast-in-supporting-role-for-netflixs-narnia-movie/
My own speculation is some kind of household servant/help or gardener or driver for the Ketterley household. I saw some suggestions for one of Digory's teachers, which I think is also plausible. I BELIEVE he was seen at a fish marketplace (though I may have misunderstood that) so maybe he's just someone Digory interacts with on the way too and from wherever it is he's going.
What I DON'T agree with is the speculation that maybe this is Frank. Much too old, much too weathered (thought I admit that can be tweaked with makeup). But I've been wrong before!
Speculate away!
I agree, there's zero chance he's Frank. He doesn't seem like he has the acting credentials for a role like that.
Even if Frank's role is reduced to it's absolute minimum, it would still likely require a few lines of dialogue and extended screen time, whereas this guys resume would indicate he's more of a "Featured Extra".
Therefore, I think you can take "Mr Potts" as a role name at face value, and would assume that his name will likely be spoken, in order to justify such a name. (i.e. he's not playing "Disgruntled Fish Monger" or "Bus Passenger #5).
Hence why I'm in the "School Teacher" camp. Or maybe a swimming instructor. Someone who has a brief enough interaction with Digory to require his name to be spoken, and for the Extra to require a screen credit.