Alexander Lebedev, the proprietor of four British newspapers, revealed yesterday that he suffered a prolonged attack of depression after years of pressure from the Russian authorities that wrecked part of his business empire.

The Anglophile ex-billionaire who, with his son Evgeny, owns the Evening Standard, three Independent titles and the television channel London Live, said that he had felt like he had failed "on everything".

A former KGB agent who became a leading liberal figure, he said he had watched Russia change "completely" in the past year. In the wake of the murder of Boris Nemtsov, the opposition politician, and reports in Mr Lebedev's Russian newspaper of clan warfare inside the Kremlin, he said he feared that the country was falling into the grip of "dark forces" operating behind President Putin's back.

Mr Putin may now be the best hope of reversing that tide, he believes, if the West abandons its attempts at "isolation" through sanctions which play into the hands of increasingly influential hardline nationalists.

"Putin is not Mugabe. This is not North Korea yet," he said.

Mr Lebedev was for years the financial muscle behind Novaya Gazeta, Russia's leading investigative newspaper, spending "$20 million" on keeping it running, but he said that he had stopped funding it because of the expense and the strain under which it placed him. "I wanted some respite. I wanted some time with the kids."

He remains a main shareholder but his decision to stop bankrolling it, "probably explains why I'm being left alone" by the authorities more. It may also underpin an announcement this week by the newspaper's editor that physical copies may cease to be printed after the May 9 victory day holiday. He was careful not to criticise Mr Putin personally. "I would rather do a caricature of the Prophet Muhammad," he said, laughing. "Who knows what is riskier now?" Mr Lebedev is one of the few oligarchs during the Putin era to have remained in Russia and spoken out against the Kremlin. Most of Russia's richest men have behaved deferentially towards the president, who yesterday publicly urged them to return offshore assets to Russia to reverse a record $151.5 billion in capital flight last year.

Mr Lebedev has suffered repeated attacks on his National Reserve Bank and in 2013 escaped a jail term after a long trial for "hooliganism motivated by political hatred" after he hit a fellow businessman on national television.

Losing most of his fortune has left him "a freer man", he said. "Having lost all of your businesses you don't have this heavy weight on your feet." He added: "I'm a freer character. It's nice not to be attacked on a daily basis."

Many people compare Mr Putin to Hitler, he said, but he believes that a better comparison would be with Hindenburg, the long-serving German leader who reluctantly appointed Hitler as chancellor and died in office a year later. "That gives a completely different picture."

He fears the rise of the ultra-conservative "Anti-Maidan" movement, fronted by Orthodox Christian bikers and thugs loyal to Ramzan Kadyrov, the Chechen leader.

Last year his world was turned upside down by illness. "I spent half a year in a serious reflection with myself," he said. "Some might call it a depression."

At one point he consulted the celebrity American psychotherapist Irvin Yalom.

"I woke up one morning in May; it coincided with what happened in Crimea and I suddenly started reflecting and I kept reflecting for six months. You have a feeling you're a complete failure. Everything you've been standing for, fighting for. Nobody cares. It's kind of an illness but it comes not from purely chemical or biological things."

To recover he threw himself into his hobby of flying, travelled with his family, played with his three children and did "lots of sport".

He has suffered attempts on his life over the years, the last of them "quite recently". He said: "It gets to you. It's not nice to jog when you are being followed by somebody."

He added that Russia was at an "important historical crossroads" and he believed that it was not too late to choose a liberal escape path.