News Corporation and 21st Century Fox chairman Rupert Murdoch has given his first in-depth interview since 2009, opening up about his divorce from Wendi Deng, the future of newspapers and the decision to split News Corp into two companies last year.

Mr Murdoch told Fortune magazine he had felt an "emotional" reluctance to split News Corporation split into two companies but had been proven wrong.

"I think it's been a great success," he said. "And I'm not talking about the share market. I think the two companies, which were all in one before, are now much more focused, which will lead to faster growth.

"Print is going through a tough time," Mr Murdoch, who recently turned 83, said. But he said it was crucial to keep investing in newspapers.

"There's got to be a lot of money spent on digitising everything," he said. "You've got to keep improving and competing in a new world, as well as keeping your old world going."

He said having cash reserves, as News Corp does, "gives you a lot of security" and surmised that the company's New York Post could become an online-only publication within five to ten years.

But he said The Wall Street Journal could remain in print for much longer. News Corp also owns The Australian.

In the interview, Mr Murdoch revealed he had learned while on a trip to Australia that his ex-wife Ms Deng had spent time at their California ranch in October 2012 and April last year with former British prime minister Tony Blair.

"When I got back, I naturally asked the staff, and it opened up," he said.

Mr Murdoch said he filed for divorce a week later, "as soon as I could find a lawyer".

The divorce from Ms Deng, who is Mr Murdoch's third wife, took place in November last year.

Mr Blair, who is godparent to one of the couple's children, has always denied having an affair with Ms Deng.

But earlier this year, Vanity Fair published extracts allegedly from Ms Deng's diary in which she waxed lyrical about Mr Blair.

Mr Murdoch said he had been "shocked" by the account in the article. "I wish we just could have got divorced quietly," he said.

"I was in an unhappy situation, and all I'm worried about or do worry about is two beautiful little girls from that marriage," Mr Murdoch said.

"And they come and stay with me a great deal. I feel like I've turned over a new page in my life."

Mr Murdoch, who refused to comment on the ongoing phone hacking scandal affecting News Corp's UK operations for legal reasons, said the past few years had been "quite stressful".

Two weeks ago Mr Murdoch's eldest son Lachlan returned to News Corp and 21st Century Fox as non-executive co-chairman, while brother James was appointed co-chief operating officer at News Corp.

Mr Murdoch said he regretted not hiring Facebook chief executive Mark Zuckerberg, who was "all for" becoming part of News Corp when it splashed $580 million to buy music-based social network MySpace in 2005. He said the company's management of MySpace was "one of our greatest screw-ups of all time".