There are several methods of producing gin, but the European Community Regulation which governs spirits defines only two.
Distilled Gin: By far the more important method of gin production, distilled gin is produced in a traditional distillation method and includes London Dry Gin and Plymouth Gin styles. Plymouth Gin is a style that by law can only be produced in Plymouth, England; it is distinctly sweeter than London Dry Gin.
The flavouring ingredients are at the core of traditional gin production; they are all natural and referred to as botanicals. The type and quantity of each producer's botanicals vary according to their own closely guarded recipes; all are carefully selected and tested for purity and quality. All gins include juniper as an ingredient, other botanicals used are coriander, angelica, orange peel, lemon peel, cardamom, cinnamon, grains of paradise, cubeb berries and nutmeg.
No.3 is the London Dry Gin distilled to a proprietary recipe by Berry Bros. & Rudd. The name No.3 refers to the address in St James’s Street, London – our home since 1698. No.3 was created to be the last word in gin for a dry martini.
Compounding: Gin can also be produced without redistilling and by instead flavouring suitable alcohol with natural substances which give a predominant taste of juniper: this method is known technically as compounding. The finest base for this 'neutral' spirit is either grain (normally barley and maize) or molasses. This type of production can be likened to that of flavoured vodka.
Sloe Gin is a sweetened style made by infusing gin with sloes (the fruit of the blackthorn).