On second thought the death of the Russian is the best solution.

But there's no hurry.

Besides," continued Inspector Val, his tones betraying that sublime appreciation of art at its utmost which an amateur of bronzes might have felt in the presence of Cellini's Perseus, "besides, I want you to take a look over this job of London Bill! You'll never again see its equal--never such perfection of plan and execution!" Richard was glad of the darkness that hid the half-smile which the delight of Inspector Val called forth.

Protest would be of no avail; it was one of those cases where to yield is the only way of saving time.
Inspector Val re-entered London Bill's tunnel and invited Richard to follow.

He showed Richard how truthfully, like the work of a best engineer, the tunnel--begun high above water-mark on the side of the drain--sloped downward until it dipped beneath the Treasury walls.