"What are we smelling people?" asks Tristan Teller, our sartorially splendid guide. "Citrus? Bark? Herbs?"
I have another sniff. I'm mostly smelling white spirit. We all take a tentative sip and in unison, the group dissolves into a comical montage of wincing and grimacing. "It's like drinking petrol," says one woman, looking like she's just licked a rancid lemon.
We're sampling Jensen's Old Tom, a reproduction of a Victorian gin recipe that was wildly popular in London in the 18th century. It's tempting to think of the current gin obsession as a new fad but it's nothing compared to the drink's popularity during Victorian times. The UK government passed five separate acts of Parliament in an attempt to control the "gin craze" – a period in the early 1700s where gin consumption among the lower classes was rampant, causing widespread drunkenness, criminality and in many cases death.
It's a far cry from the sophisticated, aristocratic air the tipple enjoys now, particularly when quaffed in its most popular form – the gin and tonic. Teller prepares us a G&T using Jensen's signature Bermondsey Dry Gin and an oddly murky, Thames-coloured tonic made by the Bermondsey Mixer Co. The combination is delicious – refreshing and citrusy with a hint of rosemary.
This gin tasting and history lesson is taking place in Bermondsey Distillery, a boutique distiller in a converted railway arch near London's Tower Bridge. In the mid-19th century, this area was a notorious slum, but it's also enjoying a renaissance and is now an up-and-coming enclave with trendy restaurants, bars and boutiques.
After the tasting, we stroll through the nearby Maltby Street Market, a buzzy laneway lined with bars and food stalls selling everything from Brazilian burritos to Belgian waffles.
This gin-themed cycling safari is run by Tally Ho! Experiences, an operator specialising in "London tours with panache". Teller is an actor and poet who lives on a boat on Regent's Canal. Today, he's flamboyantly attired in a paisley shirt, a spotted red cravat and a white trilby with a feather in it.
So far, we've cycled our vintage Pashley bikes through the backstreets of Bermondsey and learned about the area's grim industrial heritage as a centre for tanneries. The factories would buy urine and excrement from local residents and use it to treat animal hides before hanging them in the streets to dry. The stench must have been challenging to say the least.
From Bermondsey, we skirt along the River Thames, past Victorian-era wharves and warehouses that have been converted into swanky apartments and office blocks. After passing under Tower Bridge and London Bridge, we pause in front of the magnificent gothic Southwark Cathedral. Teller explains that in Dickens' time, this area was famous for prostitution, bare knuckle fights and bear-baiting (where dogs attacked captive bears). Now, it's home to a manicured riverside park filled with picnicking families.
Our last stop is Leake Street, a tunnel underneath Waterloo Station that Banksy turned into an outdoor graffiti gallery by staging a street art festival here in 2008. It's now London's largest legal street art precinct and Teller produces some spray cans so we can add our own gin-inspired design.
Overall, it's been a fascinating exploration of a lesser-known part of the capital. My only criticism is that one tasting does not a gin safari make, but this has since been rectified as the tour now uses a custom-built "GinCycle", which serves libations along the way.
After returning our bikes to Tally Ho's lock-up near Waterloo Station, we do what any newly anointed gin connoisseur would do in the circumstances – head straight to the pub.
The 3.5-hour London Gin Safari costs £55 and runs on weekends from 2pm. It includes three gin samples, two gin and tonics and a gin cocktail. See tallyho.cc
Flash Pack offers small group adventures for like-minded solo travellers in their 30s and 40s. See flashpack.com
Rob McFarland was a guest of Flash Pack, Tally Ho and Visit Britain.