"Yes but we haven't seen much of each other since the election. We probably saw more of each other than we ever thought we would during our time together. We needed time apart," he says.

The book is not short on humor such as at one point when in Chong-qing, in the southwest of China, he was asked why his eyebrows did not match his gray hair and whether he dyed them. Everyone else at the function had regulation jet-black hair.

"He was a leader of a delegation. I thought it was amusing that after my interesting talk on the European banking system this was the only thing that had exercised him," he recalls.

Darling had many dealings with bankers at the outset of the financial crisis including Sir Fred Goodwin, the controversial former chief executive of the Royal Bank of Scotland, which the UK government eventually took over. He at one stage came knocking at Darling's Edinburgh home.

Does he have sympathy for groups such as Occupy Wall Street and other similar groups in Europe who believe bankers should have gone to jail instead of receiving big pension payoffs, as in Goodwin's case?

"The rule of law is quite an important principle. I don't think subsequently you can turn round and say that collapsing a bank is now a criminal offence and therefore you should go to jail. Bad judgment is not something that is against the law.

"I understand people's anger but I think you have to bear in mind that beating everybody up may not actually be the answer in the long term."

Some argue that the banks should not have been bailed out in the first place since it just passed their liabilities on to the taxpayer and that had they been left to fail, the spoils would have been left for the stronger financial institutions to pick up.

"It depends how sanguine you think you can be about such things. I think you will find no government that would sit back and says that it doesn't really matter. If you couldn't get your money for your tube journey back home or something to eat tonight, that would be a problem."

Darling says the current situation in Europe is very problematic and that European politicians have struggled to grasp the seriousness of the situation despite the huge major precedent - the collapse of Lehman Brothers - occurring only three years before.

He thinks on balance the euro will survive but with not necessarily everyone remaining in it.

"If you had asked me six months ago, I would have said 'yes, unqualified'," he says.

Now he is not so sure but away from the eurozone, he believes other parts of the world, including China, face major challenges in the years ahead.

"The question is how long the Chinese economy will continue to grow and can the government make sure that all its people benefit from it. The problems start to arise when some people are benefiting and others are not. That will be the big challenge for the Chinese government."

He also believes that China's fate is still also heavily dependent on what happens in the West and that is why the world's second-largest economy needs to be represented at the top table of international forums.

"You are struck if you go to somewhere like Shanghai at the sheer number of containers heading for the States and Europe," he says.

"It is in China's interests that the West is in a position to buy these goods and that is why we need China at the table."