Hervé Falciani: 'HSBC Switzerland was a Tax Haven in Itself'

"There have been times," Hervé Falciani tells me, "when I've wondered if I was losing touch with reality. Could I really have seen what I saw, and revealed the things that I did, while the financial world continued as if nothing had happened?"

Falciani, sometimes called "the Ed Snowden of banking," is the whistleblower who, in 2008, committed the most momentous theft of data in banking history. The former systems engineer at the Swiss subsidiary of HSBC downloaded details of more than 100,000 potential tax evaders and made the information available to the account holders' national tax agencies. Viewed by some as a felon, by others as a martyr for justice, he has been wanted by the Swiss for seven years. Falciani, 43, can still call on two bodyguards, supplied by the French government. Today, in this secluded Paris café, he arrives alone.

HSBC has acknowledged that its Swiss arm was guilty of advising customers on evading tax. The bank's executive chairman in the relevant period was Stephen Green, who left in 2010 to become a Conservative trade minister in the House of Lords.

"Green was recently ambushed by Channel 4 News's Alex Thomson, while declaiming from a London pulpit," I remind Falciani.

"I've seen the footage. He claimed he didn't know about the malpractice in Switzerland. Is that credible?"

"It is absolutely impossible," Falciani claims, "that Stephen Green did not know. The software employed was the direct result of a commercial strategy. Validation of that strategy came from the top down. He could have said: 'I knew there was a problem, but I didn't realise how bad it was'. But to deny all knowledge? That's tantamount to saying, 'I am not a banker'. "

"Was Switzerland controlled by London?"

"What do you think?"

"An American author once declared – albeit in a moment of self-righteousness – that investigative journalism is God's work. How would you describe banking during your time at Swiss HSBC?

"As a wilderness where whatever could be done, was done."

HSBC, Falciani says, was "a tax haven in itself".

"Criminal?"

"Yes."

"How many people have been jailed as a result of your leaks?"

"One," he says. "Me."

Falciani was born in Monaco, where his father Lucien was a banker.

"He told me, when I went to his bank as a child, 'Don't steal so much as a sweet from here. If you do, I'll be sacked.' I grew up with an idealistic vision of finance."

When, I ask him, did banking go to the bad? A gradual process, he replies, "Accelerated by technology, notably the deep web."

Hervé worked for casinos, before joining the Swiss branch of HSBC in 2001. In 2006, charged with upgrading security software, he began downloading information on what he considered suspect accounts. He fled to Nice in 2008, then to Barcelona where he had himself arrested: the only sure way, he says, of bringing the data into the public domain.

Falciani served five months in prison in Madrid. The Spanish, mindful that he had exposed an estimated $200bn of fiscal fraud, declined to extradite him to Switzerland. The full, labyrinthine story, is related in his new book, Séisme sur la planète finance, [Earthquake on Planet Money] sadly unavailable in English.

His aim, he says, is to return to Geneva, facing probable arrest, then give evidence to an enquiry in Spain.

Falciani has been married twice and has one daughter. He claims he has no permanent home, but is sheltered by activists campaigning for a law to protect whistleblowers. He is collaborating with many national tax agencies, and assists the Spanish Left-wing party Podemos.

"Are you a prospective candidate?"

"No. A source of information."

His enemies have dismissed him as a chancer, looking for easy money, though there is no evidence that he ever sold data.

"I'm driven by honesty. There is something exhilarating," he says, "about revealing a truth."

"How many British names are on your list?"

"About 6,000."

"You've talked about jail cells and bodyguards; is tax evasion really that important?"

"Yes," Falciani says, "because it removes money intended for the common good."

HM Revenue & Customs obtained the files in 2010. In Britain, there has been one prosecution and £135m recovered. It's hard, I suggest, to envisage radical reform.

"The European political consensus defends the bankers," he says. "But if we get a government – in Spain, say – that fiercely attacks corruption, banks could be exposed to a point where change becomes inevitable." The current generation of bankers, he argues, "have had their time. Now it is our time. And," Falciani adds, "We have to seize the opportunity. Swiftly, and with vigour."