The child was clutching the arm of the seat, and staring at her tormentors with parted lips and terrified eyes.

For their part, they were enjoying themselves to the full.

They had found a game which afforded them the maximum of pleasure, with the minimum of effort; and just as Tinker swooped down, a cropped and bullet-headed boy in blue velvet threw a handful of gravel into her face.

She threw up her hands and burst into tears; the children's laughter rose to a shrill yell; and with extreme swiftness Tinker caught the bullet-headed boy a ringing box on the right ear and another on the left.

The boy squealed, turned, clawing and kicking, on Tinker, and, in ten seconds of crowded life, had learned the true significance of those cryptic terms an upper-cut on the potato-trap, a hook on the jaw, a rattler on the conk, and a buster on the mark.