AtD translation: Best Boy at Colney Hatch

[Mike Jing]

P238.35-239.10   “It’s too good to pass up,” he groaned aloud to Grand
Cohen Nookshaft, his spiritual adviser. “Isn’t it?”
       “I’m thinking,” said the Cohen, whose money had been in
three-percent consols for longer than he could remember, or remember why,
“I’m thinking.”
       “I’ve never understood,” said Clive Crouchmas, “why, with all the
precognitive talent around this place, no one has ever . . .” He paused, as
if seeking a diplomatic way to go on.
       “Some serious dissonance between psychical gifts and modern
capitalism, I’d imagine,” said the Cohen, somewhat shortly. “Mutually
antagonistic, you’d have to say. We also do try not to become too mental,
like some in your own shop, over this railway Concession.”
       “Were I not out here walking free amongst you all,” declared Clive
Crouchmas, “I should be Best Boy at Colney Hatch. The other night, for just
half a second, I saw . . . I thought I saw . . .”
       “It’s all right, Crouchmas, one hears this sort of thing all the
time.”

What does "Best Boy" mean here?