WATCH: The moment criminal gang stole the Portland Tiara from Welbeck Estate gallery

The 35-year-old was spared jail for her role in the theft of the £3.5 million treasure which a judge described as “culturally priceless”.

Duong was sentenced to two years in prison, suspended for 21 months, for her part in the theft from the Harley Gallery on the Welbeck Estate, in 2018.

After Thursday's sentencing, Nottinghamshire Police released damning footage showing Duong videoing the jewels in a recce mission for the raiders.

Posing as tourists, Duong and her gangster boyfriend Ashley Cumberpatch walked around the outside of the gallery in the summer of 2017.

While discussing what areas to cover, Duong jokes: “I’m going to look round to the sheep in a minute so it looks like I’m filming everything.”

Police later discovered the couple were filming key entry and exit points to the building for the gang.

Footage shows the couple inside the gallery where they film priceless jewels and artefacts.

While admiring a display case full of silverware, Cumberpatch says: “Wow, that’s mad innit?”

Duong replies: “I know, I like that.”

The couple then spend several moments excitedly ‘shushing’ each other while they film the prized Portland Tiara and matching brooch.

Duong and Cumberpatch then filmed the exterior of the gallery, including the large windows which the gang later used to enter the building.

The video was studied by the gang who used it to plan the daring break-in more than a year later.

Burglars wore motorcycle helmets, boilersuits or overalls to steal the two pieces of diamond-encrusted jewellery from the armoured glass display.

The raid, on November 20, 2018, was later linked to a series of vicious tie-up burglaries targeting footballers and other wealthy individuals in Nottinghamshire and Surrey.

Gang members Cumberpatch, 38, Kurtis Dilks, 37, and Andrew MacDonald, 44, were jailed in July 2022 for a total of more than 100 years after being hunted down by police.

Cumberpatch and others were convicted of the burglary in the original trial, as well as the burglary of the home of footballer Ashley Cole.

Duong, of Francis Street, Nottingham, was not part of the original trial but later pleaded guilty to one count of conspiracy to commit burglary at the Harley Gallery.

During the sentencing, Henry James, prosecuting, described the raid as an "heinous attack on the country's heritage" which saw three men bearing power tools break into the gallery, vault and display case, while wearing motorcycle helmets, boiler suits, overalls and gloves.

They escaped in an Audi RS5 which was later set on fire in Blidworth where they switched to a white transit van.

“Her co-defendants were on a plane and out of the country shortly afterwards,” said Mr James.

Saleema Mahmood, mitigating, said there was no evidence Duong was involved in the actual burglary and a psychiatric report described her as "impressionable”.

"She was in a relationship with her previous partner Ashley Cumberpatch where she was influenced if not physically then certainly mentally and emotionally.”

"She asks the court to be merciful and consider the impact on her children," said Ms Mahmood.

Judge John Sampson sentenced her to two years, suspended for 21 months, with 20 rehabilitation days, because there is “a realistic prospect of rehabilitation with Cumberpatch out of her life.”

Detective Constable John Wilson, of Nottinghamshire Police, said: “As we maintained all along, Duong knew exactly what she was doing when she visited this location under the guise of a day out.

“Whilst other visitors were admiring the many paintings and other treasures on display, she and Cumberpatch were callously planning a multi-million-pound heist that robbed future generations of a genuine national treasure.

“I am pleased she has now admitted to her part in this crime and that the final loose end in this multi-year investigation has now been resolved.

“Duong could not be mentioned during the earlier trial so I am pleased her involvement in this brazen crime can now be reported.”

In the early hours of 20 November 2018 three men arrived at the venue by driving astolen car through an adjoining field.

After climbing a small fence recorded in the footage, the men then smashed their way through the large windows Duong had filmed nearly a year before.

Just minutes later they left the way they came and drove off with the loot.

The tiara has never been found and is thought to have been broken up after being taken to Istanbul.

Detectives identified Cumberpatch - a career criminal well known to officers – as a suspect.

He and other gang members were later linked by their mobile phone activities to a pair of crooked jewellers in London’s Hatton Gardens.

When police raided the shop, called Paris Jewells, officers found a plastic bag containing a stash of jewellery and an FA Cup runners-up medal stolen the day before from the home of another professional footballer.

They were then able to link the shop and the gang to several other violent break-ins in which victims were tied up and assaulted in their own homes.

The gang were convicted of a string of offences, including conspiracy to commit burglary and robbery.

Cumberpatch, of Carlton, Notts., was jailed for 29 years while Dilks, of Whitegate Vale, Clifton, was jailed for a total of 35 years.

MacDonald, 43, of no fixed address, was sentenced to 32 years.

Three other gang members, Tevfik Guccuk, 43, Sercan Evsin, 28, Christopher Yorke, 52, also received jail terms for ‘converting criminal property’.