The wheat neutral spirit on which Tanqueray gins are based is produced in the rectifiers housed in another part of Cameron Bridge and is in fact the same base spirit used to make Smirnoff vodka, so extremely pure. Almost all other gin distillers buy in their grain neutral spirit from third party distillers and rectification at the same distillery gives the distillers of Tanqueray an even greater control over the consistency and quality of their base spirit.
Various brands of vodka and whisky are produced in other areas at Cameron Bridge and the focus on one centre of distilling excellence means Tanqueray benefits from a large state of the art testing laboratory where the quality of botanicals and samples from various stages of production are carefully monitored.
The move from the Laindon Distillery in Essex, which closed in 1998 (the site is now a business estate named Juniper Park), to Cameron Bridge presented something of a challenge for Tanqueray's distillers as although the stills and other equipment were moved from London, the local water was different in character. Their solution was to use two different types of water in the gin's production. Water extracted from a deep bore hole on the distillery's grounds is blended with demineralised water to mirror the character of London water. Interestingly, Tanqueray Ten is produced using only demineralised water.
Tanqueray's recipe has remained unchanged since 1830 and has three dominant botanicals: Tuscan juniper, angelica root and coriander, contributing to Tanqueuray's crisp, dry style with a rich juniper flavour. The forth botanical, liquorice, is less obvious but no less important to the perfect balance of this blend of botanical flavours. The selection and care or these botanicals is crucial to the quality of the finished gin and test distillations are continuously undertaken in the onsite laboratory to monitor these.
Some distillers believe that the botanicals should be left for a period to steep in the neutral alcohol before commencing distillation. The folk at Tanqueray are in the other camp who start to distil immediately believing that a long period of maceration is either unnecessary or even detrimental as it 'stews' the botanicals. As explained earlier, water plays an important role in the gin's final flavour. Its addition at this stage is also crucial to the distillation process. If water were not added and the botanicals distilled with just near pure alcohol (grain neutral spirit) when the distillation was completed the still would boil dry but with spent botanicals left burn on the exposed steam heating coils at the foot of the still. Adding water means that all the alcohol can be distilled off still leaving water covering the steam coils and the botanicals can be run off with this water.
Most large scale gin distillers now make their gins using a 'multiple-shot' production method, whereby a recipe of botanicals several times stronger than the original recipe is macerated and distilled to produce a super concentrated gin. This is then diluted with neutral spirit to bring the proportion of botanicals to alcohol back to that of the original recipe. This multiple-shot method saves on still usage compared to the traditional 'one-shot' method, thus increasing production capacity and saving on energy costs. One-shot distillation is now extremely rare other than in boutique distilleries and Tanqueray is one of the last major gin brands still employing this method.