Jenever can be considered one of the first Gins. Produced in the low countries since the 17^th Century, it was developed for medicinal ends. At the time, it was believed that juniper, Gins main botanical, had curative powers, and it was juniper which gave it its name (jenever being Dutch for juniper). 
Jenever is different from modern Gins because of its more limited array of botanical and dilution with malt wine, which gives it a hard, bitter flavour. 

Background
It was in Jenever that the English found inspiration for Gin. During the 80 years war, British soldiers fought alongside the Dutch against the Spanish. Before each battle, a shot of Jenever or, as it became known, “Dutch Courage”, was drunk to warm the soul. Jenever, whose name means juniper, is therefore the ancestor of Gin, and has been produced since the 17^th Century. 
The first recipe is attributed to Franciscus Sylvius, a respected professor at the university of Leiden. Recipe or prescription, because Jenever’s first uses were medicinal, mostly for kidney ailments, and not for enjoyment’s sake, like today. The attribution for its invention, however, isn’t consensual. Towards the theory that Jenever existed before, there are written references to this medicine, to Aqua Juniperi, made long before the birth of Sylvius. 
The almost exclusive use of juniper during distillation and dilution later with malt wine are two factors that differentiate Jenever from its successor, Gin. In effect, the recipes for Jenever are very sparing in botanicals, apart from the obligatory juniper, and some herbs and citrus fruits. The spotlights always stayed on juniper, though. After distillation, the resulting spirit is diluted with malt wine, the quantity of which gives further designations to different Jenevers. Jonge (young) Jenever has a maximum of 15% of malt wine and Oude (old) can have more than that. There is a third kind, Korinwijn, which is rarer, in which the percentage of malt wine is over 50%.

Distilled Gin is an ever growing group of Gins which bring a new approach to production methods, giving the Master Distiller greater freedom. 
As opposed to London Dry Gins, the technical specifications for a Distilled Gin aren’t so rigid, apart from the fact that the aromatisation must be made through a process of distillation. 
It is in this varied class that we catalogue very different Gins; those to which are added infusions of their botanicals post-distillation, those which make separate distillations of their botanicals, those which have a smaller than usual quantity of juniper, those with colour, and other myriad characteristics not permitted in the London Dry Gin class.

Background
From the Gin Acts to the 20^th Century there was a leap. London Dry became popular and became the standard for excellence. On the rocks, in gin and tonic or as the spirit base for various cocktails, it was the fashionable drink to be seen with. The 1920s brought cocktail parties to the grand hotels, substituting dull afternoon tea. In the 1950s and 60s it was rare that a Hollywood star wasn’t accompanied by a Dry Martini. They were the golden years of Gin. The 70s and 80s, however, marked a downturn in consumption. The fresh image of the vodka overtook the outmoded look of Gin, which went to sleep until the following century.
The renaissance saw new brands which brought a breath of fresh air to a centuries old spirit. Hendrick’s, born right at the turn of the century with its cucumber freshness takes was the first to hold centre stage, Martin Miller’s, its name inherited from its creator, which distils all its botanicals separately and Monkey 47, which, for the time, used an unthinkable number of botanicals, are just three of the brands responsible for the renovation of Gin.
The only thing they have in common is that they aren’t limited by the legal and aroma palate restrictions of the London Dry class. The freedom of the Master Distiller in the aromatisation of their product is almost total, the only restrictions being that they have to use distillation of their botanicals and juniper must be to some degree present. 
The Distilled Gins are therefore the Gins of the 21^st Century which bring new approaches to production methods. They were vital in the renaissance of Gin and will have a central role in its development clearly being the class with most room for progression, which will bring further innovation.

The Old Tom Gins were the natural successor to Jenever and the first Gins distilled in Britain. They were known as low quality distillations, masked with the addition of rose water, orange flower, elderflower or sugar. 
The Old Tom Gins were almost extinct but a new movement has brought them back into the spotlight. Maintaining their sweet flavour of the olden days, they are now high quality Gins and are much appreciated in cocktail mixing. 

Background
“Rome wasn’t built in a day”. Nor was Gin. During the 80 years war, British soldiers brought back Jenever. At the same time, a significant number of Flemish soldiers who fled the war, in the direction of England, began to distil their own. Homemade production saw a large increase during the reign of William of Orange. The kind liberalised distillation, making it possible for any citizen to distil his own spirit. Cumulatively, taxes were raised on imported drinks, and conditions were ripe for a boom in the production and consumption of Gin. 
Excessive consumption of alcohol, suddenly widespread, started to affect an England already with grave economic problems with a social crisis, a direct consequence of alcohol consumption, where infant mortality, drunkenness, work absenteeism and crime became common in quotidian England.
Seeking to diminish the consumption of Gin, the first Gin Act, 1736, was signed and brought in an annual tax of £50 was placed on producers of Gin. The measure was strongly contested and the population took to the streets, forcing a revision to the law. The Gin Act of 1751 took control of the whole business from production to distribution. The new law couldn’t diminish consumption and it merely went underground. There were many places where illegal Gin was sold, almost always with a black cat, Tom Cat, or Old Tom, marking the spot. Gin consumed at that time was of very low quality. It was common to use sweet ingredients to mask the quality, like elderflower which was abundant in England, or rose water. At worst, sugar was added to make it more drinkable. The designation Old Tom remained associated to low quality Gin and naturally died out once more controlled quality Gins, the London Dry Gins, became the norm. Today, however, there are several brands launching their own versions of Old Tom. They are now of unquestionable quality with a common trace of sweetness. For that reason, they are especially apt for use in cocktails, where less dilution in the Gin needs a some sweetness. 

Barrel Aged Gin is the most recent Gin class, and it brings together the gins that undergo an ageing process post-distillation. Also known as Yellow Gins, for their resultant amber colour, they are Gins with a complex aromatic profile, quite smooth and rounded. The contact with the wood of the barrel takes down the intensity of the juniper and the same time as conferring aromas of warm spices, vanilla and caramel. 
The barrels in which Gin is stored define the type of aroma profile of the finished product. Thus the choice of barrel is especially important for the entire process. Casks in which Port, Lillet or Bourbon were kept are just some examples, though some brands prefer newly made barrels.

Background
The most recent Gin class, Barrel Aged Gins is also the one most filled with history. Despite the appearance of aged gins being fairly recent, the phenomenon can be understood as a return to its roots, a step back in time to when Gin was warehoused and transported in wooden barrels. 
On the shelves in bars, supermarkets and off-licences Gin always appears in a bottle but it wasn’t always thus. Bottled Gin is relatively recent when compared to the entire history of this spirit. Effectively, it was only in the 20^th Century that all Gin was bottled. Until then, the product was transferred to barrels once made. These barrels acted as warehousing and then for transportation and retail, door to door. 
The inevitable contact of the Gin with the wood of the barrel made the Gin drunk by the end consumer a different product to that which left the distillery. This involuntary ageing process had greater effect the longer the Gin was in the barrel, and while some Gin was sold close by the distillery, some of it made long journeys, even across the Atlantic.
It was this Gin, the one that the client drank, and not the Gin straight out of the factory, that some Master Distillers wanted to reproduce. Resorting to new barrels or, mostly, barrels previously used to store and age other beverages, they submit Gin to an ageing process resulting from its contact with the wood.
The contact darkens the Gin, giving it an amber tone to a greater or lesser degree. Apart from colour, the wood influences the aromas of the Gins, conferring a greater complexity of aromas and warm notes, such as spices, vanilla and caramel.
The resulting aromas and colours are heavily influenced by what was previously stored in the barrels. Barrels of Port, Lillet, Bourbon or Sherry are just some example used in the aromatisation of the Barrel Aged Gins. For an more neutral, smoother, ageing some also use newly built barrels.

London Dry is the most widely known Gin all over the world. Juniper occupies central stage, just as defined in the technical specifications with which any Gin must comply to have the London Dry designation.
This designation defines the distillation method and characteristics of the final product, especially the level of alcohol – always higher than 37,5 volumes – the aromatisation of the alcohol, distilling only with the botanicals, and dilution only with water post-distillation.

Background
Taxes imposed by the Gin Act of 1751, the last of 8, forced a rise in the price of Gin. This price rise however had its benefits. Once the product was more expensive, better quality Gin was demanded. Gin was now sweetened with sugar to correspond to the client’s taste, and not, as previously, to mask its many imperfections.
The advances in the distillation process guaranteed spirits of better and better quality and, over time, the sweeteners were removed. Now in the Victorian age and a healthier lifestyle was in vogue, the glory days of low quality Old Tom were coming to an end and the London Dry Gins started to appear. London Dry was drier and more neutral and it was found to be more useful for mixing.
One of the inventions that marked this jump in quality was the Fractional Column Still which permitted continuous distillation, with clear gains in efficiency and surgical rectifications during the distillation process, not just at the end. New botanicals such as citrus peels, coriander seed, angelica or lily root became common in the list of ingredients used and brought to Gin new aromas, while juniper remained its top billing.

The London Dry designation determines the production method not its location. London Dry Gin can be produced in London or in any other part of the world, as long as it respects the rules which define it: 
1. It must be produced with a neutral alcohol based made from the fermentation of agricultural produce (rice, beet, cereals, grape must, apple etc.). The neutral alcohol must be as pure as possible, or rather, it must be mostly composed of ethanol, with no more than 5 grams per hectolitre of methanol in 100% ABV equivalent.
2. Aromatisation can only be made via distillation of the neutral alcohol (ethanol) with the botanicals. 
3. The spirit obtained has to contain at least 70 parts alcohol per 100 distilled. 
4. The addition of sweeteners post-distillation cannot exceed 0,1 grams per litre of Gin (final product).
5. Dilution must be made exclusively with water, the addition of colourants or aromas not being permitted. 
6. The final level of alcohol must be 37.5 vol or higher.