Here's the challenge: what word least describes an Inkling?
For Williams, the one who got me started on this slightly odd line of thought, I'd opt for 'sincere' or 'sincerity', or perhaps 'straightforward': to read his letters is to get a sense that he was always playing a role, always assuming a persona.
Applying the same technique to CSL, the word I would choose that least describes C. S. Lewis would be "vain" or "vanity". Lewis was famously free of vanity when it came to personal appearance, once describing himself as "bald and fat" and dressing in shabby clothes. And despite his extraordinary gifts (not many students get a triple first) as a writer and scholar, he seems never to have thought his talent makes him entitled to any special treatment (Janie M. still made him walk the dog and take out the trash).
For Tolkien, it's harder. "Stolid, staid" are somewhere in the right territory but inadequate. Descriptions of him make it clear there was something elusive, mercurial, almost bird-like about him, but 'dapper' needs to go in there somewhere as well.
At any rate, that's what I came up with on a first attempt. I'd be interested what descriptors others would find appropriate. Might make a good discussion topic over a meal at Mythcon.
current watching: STARSHIP OPERATORS
*which is now done, and revised, and rehearsed. whew. It ran to twenty pages but with Janice's help I've cut it down to fourteen, which is more like what'll fit into the available programming space. Though I'm sorry to see those various sections go.