Cara Delevingne's friends are said to be worried she is "out of control".

The model has always been quirky in front of the cameras, pulling faces and silly poses. But her recent behaviour as she arrived at London's Heathrow Airport has left people close to her concerned.

"Normally Cara's up for being pictured - even posing," one of the photographers told British magazine Heat. "But this time she was really weird - shouting, pushing, screaming. I think she was drunk."

The 22-year-old cart-wheeled through arrivals, then seemingly lunged at the waiting paparazzi. She also apparently tried to kick photographers in New York two weeks previously.

Friends are said to be worried that her constant travelling, working and playing has taken its toll on her, and that she is burning the candle at both ends. At the GQ Men of the Year Awards at London's Royal Opera House recently, she was photographed on the floor, hugging fashion designer Jonathan Saunders after she took a tumble.

"She runs in a fast circle," a friend said. "But lately, it seems to have caught up with her. At the GQ Awards, because everyone else was being so well behaved, Cara seemed extra out of control."

However, the blonde beauty put on a more together display as she walked the red carpet for her new movie The Face of an Angel at the Toronto Film Festival last week. It seems that Cara is focusing on her acting career and has been spending a lot of time in Hollywood networking and going out every night.

"Cara's always the last to leave the party," the friend continued. "She's a wild child and proud of it. Everyone just hopes that her partying doesn't derail her movie career before it gets started."