A man posing as someone getting ready to propose marriage has ran out of a jewellers with a diamond worth more than £20,000.
As part of the audacious ruse he called the store three days before, saying he was interested in purchasing an engagement ring.
The man with long black hair arrived for his appointment dressed in a shirt and trousers and sat opposite a member of staff.
In the footage she can be seen delicately balancing the 1.82 carat loose diamond on the man's finger.
But seconds later he puts his other hand over it, gets up and races out of the shop and into a green getaway car.
The theft took place at about 3pm on Thursday, October 12 in the King's Jewelers in Walnut Creek, near San Francisco, USA.
Worker David McConnell said the shop has been in the area for 40 years and has never seen a robbery as brazen as this one.
He said the man had called the shop "talking engagement rings" a few days earlier.
He told CBS in San Francisco : "It's a pretty routine thing and there was nothing that raised a red flag about him that we had any concern.
"We put it on his hand and he covered his hand, and turned and ran out of the store."
Police are investigating.