Police in Wandsworth are appealing for the whereabouts of a man missing since Thursday.
Officers are becoming increasingly concerned for 30 year old Lucian Bobarnac's welfare and are urging him to contact them.
He's of slim build, 5 foot 10 with shaved black hair.
More top news
He told her "If you don't be quiet I will kill you" before stealing a bangle and rings from her hand.
One of the alleged kidnappers of model Chloe Ayling is fighting extradition as his lawyer claims the entire case could be a "sham".
Uber's chief executive Dara Khosrowshahi said the company "got things wrong".