Nick Clegg is unique in British politics, say BBC's James Landale

No MP has such a cosmopolitan and international background - his mother is Dutch, his father half Russian, his wife Spanish.

In a rare interview, his mother, Hermance Clegg - who survived three years in a Japanese prison camp in Indonesia - told me that she understood the "stresses and strains" that his job brought.

"I feel proud of him. Nick is very strong," she said.

And no party leader is so disarmingly transparent.

In the latest interview in a series of BBC profiles of the party leaders, Mr Clegg talked frankly about life outside politics.

He insisted, of course, that he wanted to stay on as MP for Sheffield Hallam and Lib Dem leader and will campaign hard to do so.

But he was also prepared to contemplate what might happen if he was not successful.

"I have never thought politics is the be all and end all," he said.

Mr Clegg was also open about the tough battle the Lib Dems faced in this election.

With the party on single figures in the opinion polls, he told me that this, for the Lib Dems, would be "an election of resilience" from which the party would have to recover.

"I have absolutely no doubt that once we are through that, we will grow again in the future," he said.

The Lib Dems were "more battle hardened" than they were five years ago.

And in the face of so much criticism, from both within and without his party - "there is no point moping or you will never get anything done" - he defended his record.

Britain's economy, he said, would have collapsed like Greece's if the Lib Dems had not joined a coalition with the Conservatives.

So only days before the election campaign begins, Nick Clegg appears up for a fight.

He insists the pollsters and the critics will be proved wrong.

But when asked about the future, unlike most politicians, he is at least willing to imagine a life away from Westminster.