A rare find in the City of London

Just below St Bride’s Church in the heart of the City of London, there is a green wooden door emblazoned with “City of London Distillery & Bar” (C.O.L.D., for short).

Behind it, a flight of wooden steps drops down steeply beneath a large copy of Hogarth’s Gin Lane. In the 1751 print, created to aid the British government’s campaign against drunkenness, a mother wrecked by London gin has let her baby slip into the subterranean depths of Gin Lane. A sign on the parapet reads, “Drunk for a penny. Dead drunk for two pence”. (See the story about Hogarth’s Gin Lane on our sister site BBC Culture for more).

This is the image that welcomes visitors to the only distillery still creating London dry – a type of gin that must meet certain requirements and includes labels such as Beefeater, Bombay, Tanqueray and Gordon’s – within the limits of the City of London.

As I descended into what looks, at first glance, more like a speakeasy than a distillery, Luke Shackleton, the operations manager, was explaining the history of London dry gin to a tour group.

“London dry gin came out of an attempt to regulate what people were drinking,” he said. “In the 18th Century, gin was a cheap but very dangerous way to get drunk – it used to be laced with turpentine and sulphuric acid. People were worried by the Gin Craze that was sweeping Britain, and that worry gave rise to Hogarth’s picture Gin Lane, which we’ve got upstairs.”

As he was giving his tour, I waited in one of the bar’s antique leather armchairs. The building, probably Victorian but built on much older foundations, sits on top of the River Fleet, the largest of London’s “lost rivers”.

The distillery itself is new, however, built by gin enthusiast Jonathan Clarke in 2006 as a way of producing London dry gin within the City of London – the district in the heart of London that, from Roman times up until the Middle Ages, was where most of the settlement was located. (Other London-based labels are located in other, newer parts of the city; the Beefeater Distillery, for example, is in Kennington, on the south side of the Thames).

Perhaps surprisingly, London dry gin is manufactured all over the world. The term London dry is applied to gins that meet three requirements: they must be distilled with juniper berries, use ethanol of an agricultural origin (like grains, sugar beets or potatoes) and be bottled at a minimum of 37.5% proof.

Those regulations were laid down by the City of London 300 years ago – and so to drink London dry gin, and to watch it being made in the City today, has a sense of time-honoured pilgrimage about it.

The low-ceilinged, eccentric bar pays tongue-in-cheek homage to those past times. The bar’s over-the-counter lighting comes from seven Victorian copper kettles that have had their bottoms cut out. There’s a Beefeater Gin promotional figurine from the 1950s, a number of Edwardian-era bedpans used as wall decorations, a penny arcade pinball game and a black Underwood typewriter resting on an open bureau. It’s as if Ernest Hemingway or Ian Fleming – both great fans of gin – had just stopped work and gone in search of a martini.

In fact, the only thing that seems to be taken seriously is the display behind the bar, which has bottles of the five gins that Clarke and Shackleton make at City of London Distillery: London Dry Gin, Square Mile, Sloe Gin, Old Tom, and its newest gin, Christopher Wren. Launched 26 October 2015, Christopher Wren’s bottle shape is based on the dome of St Paul’s Cathedral; it’s also a nod to the architect’s St Bride’s Church next door.

When his bit of the tour ended, Shackleton came over to join me, dropping down heavily into the armchair opposite of mine; he was big, bearded and clad in a tweed waistcoat (the distillery’s livery). My first question for him was how Clarissa and Jennifer, the stills that produce London dry gin here, were doing. Each of these two beautiful, complex aluminium and brass column cylinders is capable of turning out 600 litres a day.

Inside the stills, vodka is boiled up to a minimum of 78.33C and forced through a “gin basket” of juniper berries, herbs, spices and dried fruit. The flavoured ethanol steam is then cooled down to produce gin at the other end.

The herbs, spices and fruit are referred to as “botanicals”, and they give each London dry gin its unique flavour. In the early days of Gordon’s Gin (launched in 1769) and Beefeater (in 1876), only a few basic botanicals like coriander seeds, angelica root, liquorice and orris root were used. Bombay Sapphire changed all that in the 1980s by using 10. Now, some gins incorporate as many as 47.

That increasing complexity and choice of flavours has been one of the reasons gin has taken off so spectacularly in recent years. There are now more than 300 high-quality dry gins being made around the world, and the City of London Distillery stocks them all (though they’re kept at the back of the bar so as not to distract visitors from the local product).

The abundance of choices makes Shackleton confident he can find a gin for everyone. “I always ask people what flavours they like – fruit, floral, spicy, earthy, savoury, citrus. Depending on what they say, I reckon I can find them a gin they’ll like,” he told me. That’s also why, apart from Fevertree, the bar doesn’t stock the flavoured tonics that are becoming increasingly popular mixers. With so many gins to choose from, they don’t need to.

To make the most of the flavour, Shackleton suggested that gin and tonic be served with cubed ice, not crushed, which dilutes the taste.

Unsure if you’re drinking a high-quality gin or not? If you taste ethanol, Shackleton told me, it’s a poorly made gin. “But that’s rare. In any case, there should be no right or wrong when it comes to taste because every individual – and every gin – is so unique,” he said.

Even clarity, once a sign of a properly-produced gin, is no longer necessarily a mark of quality. “As more and more people are looking to do something new, we are now seeing cloudy gins,” Shackleton said. “It doesn't alter the flavour. It is about how much organic material is carried through in the distillation process.”

“If you like drinking it, it’s a good gin.”

This story is a part of BBC Britain – a series focused on exploring this extraordinary island, one story at a time. Readers outside of the UK can see every BBC Britain story by heading to the Britain homepage; you also can see our latest stories by following us on Facebook and Twitter.