Colour supplement piece glued into a scrapbook circa 1979 - the author is possibly Keith Waterhouse. 

Attempts to put these prank tactics into practice - in the elevator at Dillons, in department stores - led to underwhelming results. Perhaps grown-ups instinctively tune out the prattlings of children. Perhaps we weren't good enough actors. 

Conversely, eavesdropping rarely trawls up anything very startling or surreal.