Unbalanced Vision

It may be illegal to whistle in bookshops. My boss said that a few years ago an assistant at some London bookshop got sacked for whistling whilst working. On Monday a sensible-looking man came in the shop and whistled a tune in a loop for quite some time. Later after he left my boss quipped, 'You're allowed to whistle only if you buy our books'. Of course the man walked away empty-handed.