In February last year 100m euros (£65m) worth of diamonds vanished from vaults under the Belgian city of Antwerp during a heist which was straight out of the Hollywood movie Ocean's Eleven.
By Chris Summers
BBC News Online
Detectives believe an Italian gang were responsible but the stones are still missing and may never be found.
Ever since the beginning of the 16th century Antwerp has been the world's diamond-cutting capital.
Over half the world's diamonds are traded in the Belgian city's gem district, a maze of streets close to the train station. Diamond merchants in Antwerp have a combined annual turnover of $23 billion.
Rough diamonds arrive from all over the world and are placed in vaults as deals are done.
World's biggest robberies
Apr 1945: Reichsbank in Berlin, Germany looted. Estimated £2.5bn stolen.
Feb 2003: £65m diamond robbery in Antwerp, Belgium
Jul 1987: £60m robbery at Knightsbridge safety deposit centre, London
1994: £29m gems raid in Cannes, France
Nov 1983: £26m Brinks Mat robbery at Heathrow, London
Jan 1976: £22m robbery at British Bank of the Middle East in Beirut, Lebanon
Source: Guinness World Records
As well as diamonds mined in South Africa, Australia and Russia there is also a thriving black market in so-called "conflict diamonds" from Sierra Leone and the Democratic Republic of Congo.
On the weekend of 15/16 February 2003, as the city's attention was distracted by the Diamond Games tennis tournament - won by Venus Williams - the Antwerp Diamond Centre became the scene of the biggest gem robbery in history.
The raid is believed to have been carried out by a gang of veteran Italian robbers, known as The School of Turin.
The gang managed to bypass cameras, bars and 12-inch thick reinforced doors to gain entry to the vaults.
Joris Van der Aa, a journalist with the Antwerp newspaper Het Laatste Nieuws, said: "They had copies of the keys made to get in; they bypassed the alarm system and they replaced the CCTV tapes so it made it look as if nothing was going on inside the vault.
"These guys never use violence. They are brilliant with keys and alarm systems and don't need to resort to violence."
Mr Van der Aa said: "It was the perfect crime. These guys are professionals. Most of them are quite old and they all have these nicknames. One is called the King of Thieves, another one is known as The Magician With The Keys."
After prying open 123 vaults they were so loaded down they gave up on the remaining 37.
One diamond dealer told BBC News Online: "There has never been such a robbery in the history of the trade in Antwerp and everybody was over-confident about security."
Bags dumped in ditch
The police got their best lead when they found several discarded bags in a ditch beside the main road out of Antwerp. Inside was, among other things, a half-eaten sandwich. Police say they obtained vital DNA left behind by one of the robbers.
The vault was ransacked
The man facing trial over the theft is Leonardo Notarbartolo, who had rented an office in the Antwerp Diamond Centre in November 2000.
Antwerp's director of judicial services, Eric Sack, said Mr Notarbartolo worked as a diamond merchant in the centre and paid several visits to the vault deep underground.
Mr Notarbartolo, 51, is not believed to have taken part in the actual robbery itself but he has been charged with serious theft, membership of a criminal group, use of false keys and false documents.
The wheels of Belgian justice turn slowly and his trial is thought to be some way off.
The alleged leader of the gang, Antonino Finotto, is believed to be in Italy. His DNA was allegedly found inside the vault.
Search led to Italy
Not long after the heist Belgian detectives contacted their counterparts in Turin.
Mr Van der Aa takes up the story: "Italian police searched offices in Turin and found a few diamonds in a safe. They had certificates (of authenticity) with them.
"They photographed the diamonds and sent the pictures to the police in Antwerp.
Keys were copied to gain entry
"Antwerp police believed they were from the heist and two weeks later they went to Italy to take back the diamonds. But when they opened the safe they were all gone."
Will the Antwerp diamonds ever be found?
London diamond dealer Michel Einhorn, whose aunt was among the victims of the robbery, said he understood most of the diamonds which were taken were already cut and polished.
He told BBC News Online: "Some would have been laser inscribed, but not all of them, and even if they are that can be removed."
Mr Einhorn, who has a shop in Hatton Garden, said: "Reputable dealers will not buy diamonds from anyone without checking them out.
"But unfortunately there a few places around here, and in Antwerp and Amsterdam, with an unsavoury reputation. There will always be people willing to buy these diamonds."
So how can the average person know if the diamond ring they are buying was made with a stolen stone?
Mr Einhorn said: "It's like buying anything. If you buy it in a pub from a guy whole looks dodgy then that's your look out. But if you buy it from a reputable trader, for example someone who is a member of the London Diamond Bourse, you're pretty safe."