Princess Beatrice and Dave Clark enjoy a night out with James Middleton's girlfriend Donna Air

and her boyfriend

enjoyed a night out with

's girlfriend,

on Thursday. Having attended the Butterfly Ball in Battersea Evolution

joined

and

as the trio headed to LouLou's nightclub to let their hair down.

, 24,

kept her look simple with a black dress, jacket and shoes, adding a touch of sparkle with a glittering bag. Beatrice and Dave, who has been her boyfriend for more than six years, strolled hand-in-hand to the club previously frequented by

' sister

and her husband

.

also chose an all-black ensemble,wearing a floor-length Luisa Beccaria dress detailed with sheer sleeves as well as a low back. Taking a leaf out of

's style book

also carried a striking gold clutch.

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Private members club LouLou's is also the same venue where

and

were first debuted their romance. In April, businessman

, 27, was photographed hand-in-hand with TV personality

, 33, who looked coy as the cameras captured their moment together.

did not join his new girlfriend on Thursday but

's night out with his brother-in-law's cousin is a sign of their blossoming friendship.

and her sister

enjoy a good relationship with

and the trio recently stepped out at an exclusive Mayfair restaurant to toast socialite Heather Kerzner's 44th birthday.

The gathering, which was held at Downtown Mayfair, was a sure indicator that the Middleton family members have been warmly welcomed into the royal fold, as

seems to be as well. Earlier in the evening

attended The Butterfly Ball: A Sensory Experience with

's mother,

. The event, in aid of the Caudwell Children's charity, also drew famous faces including,

,

and designer

."Lovely night at the Butterfly ball 4 Caudwell Children's Trust," tweeted

with a snapshot of herself and

. "With @SarahTheDuchess, @johndcaudwell and @cla1re24!""Really excited to come!" said

before she headed to the glamorous ball. "What a great Charity xx."