The name London refers to the capital of England but the gin is not confined to the metro. In short, the product is not restricted to geographical limits, unlike champagne, scotch, and tequila which are geo-restricted. Champagne is produced in India but it cannot be called as such since the production is not in the Champagne district of France.
London Gin has thus become a standard and precedes other spirits of the same style as far as a yardstick of qualitative measure is concerned. It is the attributes that have accorded the product this style status, the flavor, aroma, distillation process, blending, and yes the consumption rate act as accreditation.
The spirit is named by its variant and not by its place of origin. London gin is a dry variety like Osel from Estonia and this liquor is vastly popular and trending. It is often consumed with Indian Tonic. Of late there is a resurgence in the popularity of this alcoholic spirit and it is being called the gin boom.