Jessie J's gig at aN-Dubzrapper Fazer and The Only Way Is Essex star Lauren Goodger were seen later giving evidence to the police, after the injured man was taken out of the club on a stretcher, covered in blood.
A Scotland Yard spokesperson told PA: "At around 12.07am the ambulance service called police regarding a man injured in a club off Southwark Street.
"He is thought to be in his 30s and has been taken to hospital in a serious condition. The victim is thought to have been injured with a bottle."
The police statement also confirmed that the offender had been arrested and was being held in custody.

Blackberry UK have since commented on the episode, saying in a statement: "A serious incident occurred at our BlackBerry event tonight. Our first concern is the wellbeing of the injured guest.
"We are doing all we can to assist police with their enquiries and are unable to provide further comment at this time."
Jessie J also took to Twitter after learning of the attack, posting on her official page: "My thoughts are with the person who was seriously injured last night at the blackberry bbm party. So sad. I really hope they are ok."

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