Just William by Richmal Crompton

William went whistling down the street, his hands in his pockets. William's whistle was more penetrating than melodious. Sensitive people fled shuddering at the sound. The proprietor of the sweet-shop, however, was not sensitive. He nodded affably as William passed. William was a regular customer of his -- as regular, that is, as a wholly inadequate allowance would permit. Encouraged William paused at the doorway and ceased to whistle.

" 'Ullo, Mr. Moss! " he said.