Terry-Thomas was an English character actor and comedian who became internationally known through his films during the 1950s and 1960s. He often portrayed disreputable members of the upper classes, especially cads, toffs and bounders, using his distinctive voice; his costume and props tended to include a monocle, waistcoat and cigarette holder. His striking dress sense was set off by a 1⁄3-inch (8.5 mm) gap between his two upper front teeth.

A diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to as gap teeth or tooth gap.