Seven alleged fraudsters are going on trial in Paris accused of impersonating a French minister to trick wealthy victims out of more than €50m (£42m).
Investigators say the scam involved a fake Jean-Yves Le Drian - now French foreign minister - requesting funds by phone and Skype for a "secret mission".
The alleged masterminds are two Franco-Israelis: Gilbert Chikli, 54, and Anthony Lasarevitsch, 35.
Ismaili Muslim leader the Aga Khan and a Turkish tycoon were allegedly conned.
At the time Mr Le Drian was defence minister and not especially well known internationally - a fact that apparently made the fake more believable. The money was often said to be for ransom payments to hostage-takers, or anti-terror operations.
In meetings arranged on Skype, one of the the fraudsters wore a custom-made Le Drian mask and sat in a facsimile of Le Drian's ministerial office, complete with flags and a portrait of then-President François Hollande.
The gang allegedly approached more than 150 prominent figures and organisations in 2015-2016, including King Philippe of Belgium, Gabonese President Ali Bongo, the CEO of the Lafarge cement company, church leaders and charities. In all but a few cases the targets did not fall for the gang's hoax.
The two chief suspects were extradited to France from Ukraine in 2017.
Mr Chikli and Mr Lasarevitsch deny the charges. According to Mr Chikli, somebody else carried out the fake Le Drian scam.
The Aga Khan parted with €20m, AFP news agency reports, €7.7m of which could not be recovered. Turkish businessman Inan Kirac allegedly wired more than €47m, and Château Margaux vineyards lost €3m.
Prosecutors say evidence was found on the mobile phones of Mr Chikli and Mr Lasarevitsch, after their arrest in Ukraine, suggesting that they planned to impersonate Prince Albert II of Monaco next. There were mobile phone pictures of a silicone mask of Prince Albert.
Six of the seven defendants are charged in connection with both the Le Drian hoax and the Prince Albert plot.
In a French TV interview in 2010, Mr Chikli described previous scams, saying "you've either got the gift or you haven't, it's like famous actors.
"When it comes to me, you can say that I have a gift."