A UK court has convicted a woman of stealing millions of pounds worth of diamonds from a high-profile London jeweller.

       Lulu Lakatos was sentenced to five-and-a-half years in prison after a jury at Southwark Crown Court found her guilty of conspiracy to steal.

       In 2016, Lakatos had secretly swapped seven pebbles for diamonds worth ￡4.2 million (€4.9 million) in an audacious heist at a luxury store in London’s tony Mayfair district.

       Lakatos, who was born in Romania, was part of an international gang that fled to France after stealing the diamonds from Boodles on New Bond Street. The gems have not been recovered.

       In the days leading up to the heist, the criminals held a series of meetings with Boodles staff on the pretence that they represented a wealthy Russian investor who was looking to purchase gems, police said.

       The court heard how Latakos had then posed as a gem expert named "Anna" who then went to Boodles to value seven diamonds for the buyer.

       After she had inspected the diamonds -- which included a 20-carat heart-shaped gem valued at more than ￡2.2 million (€2.6 million) -- the jewels were individually wrapped and placed in a locked bag.

       But when Boodles’ own expert became suspicious the next day, the bag was X-rayed and the store discovered nothing but "seven garden pebbles".

       According to prosecutors and security camera footage, Latakos had used "sleight of hand" and distraction to swap the bag containing the diamonds for an identical one with pebbles inside.

       After leaving Bootles, she had handed the bag to a female accomplice before ditching her disguise and fleeing by train to France, where she lived.

       "This was an audacious theft, carried out in plain view of experienced and professional staff at a renowned jeweller," said Detective Sgt. William Man of London’s Metropolitan Police Service.

       "The meticulous planning and execution of this theft reveal to me that those involved were highly skilled criminals."

       Latakos was arrested on a European warrant last September and extradited to the UK to stand trial.

       Two men who worked with Lakatos had previously pleaded guilty to conspiracy to steal and were sentenced to three years and eight months in prison, respectively. Police are still investigating the involvement of two other women.