The London private members club scene is arguably the most prestigious in the world.

Earlier this year Business Insider compiled a ranking of the capital's most exclusive members' clubs, and found that one was particularly intriguing.

5 Hertford Street is so exclusive that it declined to give even a ballpark indication on the cost of membership.

We were instead sent one photo of the bar at its downstairs nightclub called Loulou's, which only left us wanting to see more of what actually goes on down there.

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Loulou's pièce de résistance is the stunning cocktail bar, where a gin & tonic will reportedly set you back at least £20. Instagram/misselp

Its Instagram account is also private. But after some digging, we've managed to put together a rare glimpse behind the scenes at the only members' club for those in the know, including Lupita Nyong'o, George and Amal Clooney, Mick Jagger and Leonardo DiCaprio when they're in London, as well as young royals Prince William and Princess Eugenie.

So if you're curious as to where the young, rich, beautiful and connected head to after hours, keep scrollin'.

Perched on the corner of Shepherds market, in London's Mayfair, behind an unmarked maroon door sits this secretive and exclusive private members' club. Royals, billionaires, and A-listers are all known to frequent the club — when they can get a reservation.

5 Hertford Street

It's owned by Robin Birley an English businessman the son of Lady Annabel Goldsmith and night club owner Mark Birley. Birley, who has now also inherited his father's private members' club Annabel's, also owns the upmarket sandwich chain Birleys. 

Step inside and you will find quintessentially English clashing patterns and prints on the carpets and walls — the club's trademark style — reminiscent of an eccentric upper-class country home. Fashion designer Rifat Ozbek is behind its boho-chic interior.

Something charming about a very English staircase #5hertford #London #interiors #patterns

A post shared by Sara Jane Ho (@sarajaneho) on Sep 5, 2016 at 2:04pm PDTSep 5, 2016 at 2:04pm PDT

Eclectic art lines the walls of the various living and sitting rooms which are lit by cabaret-style table lamps. Expect to see members wandering around in smoking jackets, velvet slippers and signet rings.

Appreciate me because I won't depreciate; NY Pt. 2 in Bio

A post shared by 1ord Arta (@1ord_arta) on Jul 21, 2017 at 2:02pm PDTJul 21, 2017 at 2:02pm PDT

There are plenty of chandeliers, some more unusual than others.

Facebook Conor Thomson Moore

Almost every room is equipped with a roaring fireplace, offering the perfect spot for a cosy nightcap, or TV dinner.

TV dinners 🍣 @nataliekyria #5hertford #thefourthings #hamachi

A post shared by The Four Things (@thefourthings) on May 27, 2016 at 3:19am PDTMay 27, 2016 at 3:19am PDT

Source: Vogue. 

There are various private dining rooms for long lunches, which dogs are apparently welcome to join.

Amazing @inesienejewellery #lunch at #5hertford #jewellery #inesiene #danaecollection

A post shared by Monica De Tomas (@monimoleskine) on Jun 26, 2014 at 4:21am PDTJun 26, 2014 at 4:21am PDT

...Or lavish celebratory dinners by candlelight.

#5hertford #birthdayextravaganza

A post shared by Fab Nap (@fabri_n) on Nov 22, 2014 at 4:21pm PSTNov 22, 2014 at 4:21pm PST

The club has its own cigar shop, naturally. And it appears that guests are welcome to chomp on one while sampling the extensive cocktail list. The gin fizz apparently comes highly recommended.

5HS's cigar bar #5hertford #thursdaynight #membersclub #loulous #birleys #cigarbar #nightlife #mayfair #london #bar #instabar #negroni #vodkasoda #cocktails #mixology #instadrinks #lifestyle with @5hertfordstreet @birley_cigars @loulous_5hertfordstreet

A post shared by Vincent's - Art & Lifestyle (@art88lifestyle) on May 4, 2017 at 4:45pm PDTMay 4, 2017 at 4:45pm PDT

Source: Vogue. 

But the real fun starts down a steep staircase to 5 Hertford Street's famed Loulou's nightclub, one of the best kept secrets of the capital's rich and famous.

The start to a good evening

A post shared by 5 Hertford Street (@5hertfordstreet) on Oct 7, 2015 at 11:14am PDTOct 7, 2015 at 11:14am PDT

Loulou's is renowned for its dimly-lit Parisian Bohemian decor and its giraffe mascot.

One of the best restaurant/bar I have been to in London which was designed by Rıfat Özbek. Private Members Club only, thanks to my dear friend @ipekbenihasim for the reservation and her company. Such a great night 👍👍👍 #loulous #london #privatemembersclub #uk #england #designedby #rifatözbek #loulous #5hertfordstreet #5hertford #mayfair #londra #ingiltere #hertford #food #dinner #lounge #cigarclub #club #dance

A post shared by FIRAT FIDAN (@allaturka) on Nov 9, 2016 at 6:45pm PSTNov 9, 2016 at 6:45pm PST

 Source: Evening Standard

Harry Styles is apparently a fan of the club — when he manages to charm his way through the door, which is apparently not all the time. Here he is posing with Loulou's giraffe.

Facebook/One Direction Hungary

As are Hollywood A-listers, including Lupita Nyong'o, George and Amal Clooney, Mick Jagger, Leonardo DiCaprio, and Margot Robbie, who are all known to drop in for dinner, drinks or dancing when they're in town.

#cantstopwontstop Documentary @diddy 👏🏽 @lupitanyongo 👏🏽 @purplepr Great night.

A post shared by Reggie Yates (@regyates) on May 17, 2017 at 10:19am PDTMay 17, 2017 at 10:19am PDT

  Source: Evening Standard

Fahionistas favour the venue for launch parties and events. Below, supermodel Bella Hadid attended a Marc Jacobs event at Loulou's.

@bellahadid @thelovemagazine @marcjacobs #ImmersiveCult #AitorSantomé

A post shared by AITOR SANTOMÉ (@aitorsantome) on Aug 10, 2017 at 5:03am PDTAug 10, 2017 at 5:03am PDT

The young royals including Prince William, Kate and Princess Eugenie, who was snapped on her way in below, are all big fans of Loulou's.

#HRH #princesseugenie of #york wearing a lovely #EthanK #calamansigreen #shinycroc #minaudiere #clutch to #5hertford #loulou's in #mayfair #London !! #Thankyou for being so #supportive !! #designer #bespoke #royals #princesseugenieofyork #jackbrooksbank

A post shared by Ethan Koh (@iamethankoh) on Jun 25, 2014 at 4:17pm PDTJun 25, 2014 at 4:17pm PDT

Source: Evening Standard.

It's really not hard to see the attraction of the club's dimly-lit, moulin rouge vibe, where it's easy to imagine all sorts of debauchery goes down after hours.

We love LouLou's 💗💗#loulous#5hertfordstreet#5hertford#londonfashionweek#luxurylife#luxurytravel#londonluxury#mayfair#mayfairhotel#ootd#luxurylife#luxuryliving#finedining#membersonly#bondstreet#hydepark#londonrealestate#servicedflatslondon#hermes#padlondon#sothebysrealty#luxuryrealestate#londonlettings#viplondon#luxlondon#fashioncapital#travelblog#barolo#pomerol#romance

A post shared by Serviced Flats London✨CandiceB (@servicedflatslondon) on Feb 6, 2017 at 8:21am PSTFeb 6, 2017 at 8:21am PST

Even the ladies' loos are a rather dramatic affair, taking boho-chic theme to another level.

Wow! Seriously dramatic ladies' room here at 5 Hertford. So glad I've got my high drama leather biker leggings and high heeled boots on...plus the one shoulder All Saints top on! #hwc #embracingdrama #allsaints #5hertford

A post shared by Harriet Waley-Cohen (@harriet_wc) on Dec 13, 2016 at 2:21pm PSTDec 13, 2016 at 2:21pm PST

Loulou's pièce de résistance is the stunning cocktail bar.

Earlier that night #loulous #5hertford #londonstyle

A post shared by please.me (@misselp) on Nov 3, 2013 at 9:44am PSTNov 3, 2013 at 9:44am PST

A gin & tonic there will apparently set you back about £20. 5 Hertford Street declined to provide a ball-park figure for the price of membership. Instead, it said that membership is gained through application only and a price given upon request.

5 Hertford Street

 Source: Evening Standard

Read the original article on Business Insider UK. Copyright 2017. Follow Business Insider UK on Twitter.

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