The robbery took place on May 25 last year on Kew Road.
Two men visited the jewellers after making an appointment and posing as customers, before tying up the manager and filling a rucksack with £1.3 million of high-value watches.
Specialist Flying Squad detectives from Met Police analysed CCTV footage, which led to the conviction of Mannix Pedro, 37, who organised the raid.
Pedro was found guilty of conspiracy to rob at Woolwich Crown Court on Wednesday (February 19) and will be sentenced at a later date.
The jury failed to reach a verdict in relation to a second man, with a re-trial set to take place at a later date.
The force was able to use footage to identify the car the men had arrived in.
The two men were also linked to three other men believed to be involved in planning the robbery, with investigations into the incident ongoing.
27-year-old manager Oliver White from Surrey was found dead a day after the incident with his mother Amy Keane describing his death as a “devastating loss” for the family.
A full inquest into Oliver’s death is yet to take place.
In a tribute to her son Amy said: “I would describe Oliver as a huge character, very warm and a brilliant person. He lit up the room when he entered it and was incredibly kind and caring, he would go above and beyond for anyone. He cared deeply for his family, was a wonderful role model for his little brother, as well as his two sisters.
“Oliver really wanted to make something of himself, he aspired to buy a house, have a family and was planning for his future and this influenced his decision to work 24/7 as he saw his friends doing well in a business they enjoyed.
“We know Oliver to be trustworthy and honest. Given the jury have convicted a man of planning and organising the robbery of Oliver, we take this as vindication of our firmly held belief he played no role in this offence and was not implicated in any involvement.
“We are all absolutely devastated with the loss of our funny, thoughtful and kind son Oliver, our lives will never be the same and we feel this loss every minute of every day.”
Detective Sergeant Matt Hollands, who led the investigation, said: ”This was an audacious robbery that was several months in the planning. I’m pleased our investigation has resulted in a dangerous offender being convicted.
“Our work is far from over, and our focus remains finding the three other men involved and putting them before the courts.”
Police continue to make enquiries to locate the three other members of the group and are urging anyone with information on their whereabouts to call 101, quoting the reference 01/MP/11200/24.
Information can also be reported anonymously by contacting Crimestoppers on 0800 555 111.
Samaritans are here day or night, 365 days a year. You can call them for free on 116 123, email them at jo@samaritans.org, or visit www.samaritans.org to find your nearest branch.
Detective Sergeant Hollands added: “Throughout this investigation Oliver has been in our thoughts and we have remained committed to securing justice for his family. His death is a tragic reminder that crimes such as robbery have a significant impact on victims.”
