In the strength of that conviction he committed a fault of tact.
He allowed himself a little conceited laugh, and repeated: "Trust me for that, sir." This was too much for the forced calmness under which the Assistant Commissioner had for upwards of eighteen months concealed his irritation with the system and the subordinates of his office.

A square peg forced into a round hole, he had felt like a daily outrage that long established smooth roundness into which a man of less sharply angular shape would have fitted himself, with voluptuous acquiescence, after a shrug or two.
What he resented most was just the necessity of taking so much on trust.
At the little laugh of Chief Inspector Heat's he spun swiftly on his heels, as if whirled away from the window-pane by an electric shock.

He caught on the latter's face not only the complacency proper to the occasion lurking under the moustache, but the vestiges of experimental watchfulness in the round eyes, which had been, no doubt, fastened on his back, and now met his glance for a second before the intent character of their stare had the time to change to a merely startled appearance.
The Assistant Commissioner of Police had really some qualifications for his post.

Suddenly his suspicion was awakened.

It is but fair to say that his suspicions of the police methods (unless the police happened to be a semi-military body organised by himself) was not difficult to arouse.