Amy Winehouse upset the king of the Zulu nation at a private party in London on Wednesday (August 4), it's been reported.

The singer was accompanied by boyfriend Reg Traviss to the launch of a new African-themed restaurant in Camden.

But she upset guests, including Goodwill Zwelithini – the guest of honour – with her apparent drunken behaviour.

According to The Sun, Winehouse failed to stand when the king entered the room and also fell asleep during his speech.

A source said: "It was embarrassing. Amy was in a state. People were cringing.”

The incident came just 24 hours after Winehouse went on a reported 16-hour drinks bender, which ended at 9am on Tuesday morning (August 3).

The singer was also said to have clashed with actress Mischa Barton during her night out.

(by Jason Gregory)