AT 42, Avenue Foch, the tree-lined boulevard that is one of Paris’s most expensive streets, looms a five-storey private mansion complete with disco, spa room, hair salon, gold- and jewel-encrusted taps, lift, pastel pink dining room and a breathtaking balcony-view of the Arc de Triomphe.

Local people always knew when there was about to be a visit from its 41-year-old ‘playboy’ resident, Teodorin Obiang, eldest son of the autocratic president of Equatorial Guinea. Days before Obiang Jr’s private jet touched down, two massive lorries would pull up outside and disgorge a sea of fresh flowers to dress the interior of the mansion.

When Obiang was in residence, passersby would see a parade of couturiers from Paris’s top design houses waiting to be admitted for fittings before returning with vanloads of made-to-measure clothes. Crates of the most expensive burgundy were another regular delivery.

On one occasion 15,000 DVDs were hauled in on wooden pallets.

But the most public statement of opulence was the fleet of luxury, turbo-charged sports cars, parked in garages or in the cobbled courtyard.

“The noise-factor was extreme,” one local said. “He seemed obsessed with security so when he wanted to go out between midnight and 2am, he’d order the chauffeur to warm up four cars so no one knew which he’d take. Can you imagine the noise of Ferraris, Porsches and Maseratis all running at once? Then he’d come down and decide to take a fifth car and that would have to be started.”

But the courtyard has fallen quiet, the mansion empty of occupants. Three months ago, in a morning raid, French police towed away 11 luxury cars.

The raid was the first in the landmark French inquiry known as the case of the ‘ill-gotten gains’.

In an unprecedented move, three serving African leaders and their families are under investigation in Paris over whether they embezzled state funds to acquire vast assets in France including bank accounts, Riviera villas and fleets of luxury cars.

The clan of Gabon’s late leader Omar Bongo and its current leader, his son Ali Bongo, the Congo-Brazzaville leader, Denis Sassou-Nguesso and his family, and President Teodoro Obiang of Equatorial Guinea and his clan are accused of having assets worth 160 million euros in France, from penthouses and villas to bank accounts and luxury car fleets.

The leaders and their families have denied building up personal wealth in France through embezzlement, money-laundering and misuse of public funds. Judges are beginning the detailed task of trying to prove such spectacular wealth was directly siphoned from the coffers of the oil-rich states to the detriment of populations left to live in misery.

With billions of dollars worth of assets of Muammar Qadhafi frozen by the UN and member countries, and other moves to recover the wealth of deposed autocrats such as Tunisia’s Zine al-Abidine Ben Ali and Egypt’s Hosni Mubarak, the drive to seize billions plundered by corrupt leaders has never been higher. But the French case against three serving African leaders, initiated by anti-corruption NGOs as part of a long legal battle, illustrates the limits on western willingness to act against rulers still in power.

“With deposed heads of state after the Arab Spring, there was no problem, the whole community was scandalised at the plundering of money from their countries. We’re warning against double standards: why should you have to wait for a leader to fall to put a stop to corruption?” said Maud Perdriel-Vaissiere, head of Sherpa, one NGO leading the case.

The police inquiry has given an unprecedented insight into the lifestyle of certain African leaders. When the spectacular art collection from the homes of the late fashion designer Yves Saint Laurent went up for auction in Paris in 2009 it was called the art sale of the century and raised more than 370 million euros. French authorities later revealed that Obiang Jr bought 109 lots at the sale, costing 18 million euros. — The Guardian, London