French investigators went to crazy lengths to make sure Google didn't catch wind of their tax investigation

The French financial authorities went to some pretty extreme lengths to ensure that Google didn't get tipped off early about its tax investigation into the Californian tech giant.

The direction générale des finances spent a year quietly looking into Google's tax affairs in the country, before launching a surprise raid on its Paris offices at 5AM (local time) on May 24. France may now try and claim back as much as €1.6 billion in allegedly unpaid taxes from Google.

The raid has apparently been a year in the making, and involved 100 investigators. Financial prosecutor Éliane Houlette gave a (French-language) interview to Europe 1 about how how they kept it a secret. (We first saw the interview over on TechCrunch.)

So how did they manage it? The 100-strong team worked almost entirely offline. "We've worked offline on this investigation for nearly a year," Houlette said. "We used one computer, but only as a word processor."

The investigators also didn't even refer to Google by name, instead giving it a codename to obscure what they were working on. "In order to protect this secret, we decided that we would give another name to Google and never pronounce Google's name - Tulip."

Investigators have been left with huge quantities of data, numbering in the terabytes - perhaps even more than the Panama Papers leak, Houlette said. She was referring to the leak of vast troves of confidential data from offshore law firm Mossack Fonseca published earlier this year that journalists and activists have alleged show evidence of aggressive tax avoidance.

She also reaffirmed that France does not intend to make a deal with Google - suggesting the case could go to trial.