Leonardo Notarbartolo strolls into the prison visiting room trailing a guard as if the guy were his personal assistant. The other convicts in this eastern Belgian prison turn to look. Notarbartolo nods and smiles faintly, the laugh lines crinkling around his blue eyes. Though he’s an inmate and wears the requisite white prisoner jacket, Notarbartolo radiates a sunny Italian charm. A silver Rolex peeks out from under his cuff, and a vertical strip of white soul patch drops down from his lower lip like an exclamation mark. In February 2003, Notarbartolo was arrested for heading a ring of Italian thieves. They were accused of breaking into a vault two floors beneath the Antwerp Diamond Center and making off with at least $100 million worth of loose diamonds, gold, jewelry, and other spoils. The vault was thought to be impenetrable. It was protected by 10 layers of security, including infrared heat detectors, Doppler radar, a magnetic field, a seismic sensor, and a lock with 100 million possible combinations. The robbery was called the heist of the century, and even now the police can’t explain exactly how it was done. The loot was never found, but based on circumstantial evidence, Notarbartolo was…