Since the first series aired, Lord Sugar has trusted him to grill candidates during the interview stage in the show's semi-final episode. His no-nonsense attitude is renowned - and he frequently pushes the candidates into revealing more about themselves than they might wish.
Littner has long advised Lord Sugar beyond the TV board-room. For the past 25 years, he has intermittently worked with Sugar and currently co-chairs a number of his companies. And when Sugar chaired Tottenham Hotspur, Littner acted as its chief executive from 1993 to 1998.
Littner is well accustomed to his grizzled lordship's refusal to tolerate fools - he has similar traits.
So Claude Littner is probably an ideal candidate to partner Alan Sugar, knowing him as well as he does. What, then, does it take to get into his good books?
"I've developed a relationship with Alan Sugar," Littner says, "whereby he trusts me and I trust him.
"Alan doesn't require anything that anyone else wouldn't require in the same situation. You need to be very honest and very straight, and, if you don't know something then say you don't know it. And if you do know something, he's very interested in hearing what you've got to say.
"I don't know what perceptions people have about him, but he's very direct, he's very straight, very clever and astute and he doesn't like - to put it in his words - bull****ers."
And yes, Claude Littner can confirm, "what he doesn't suffer, is fools. If you just want to say something for the sake of saying something, or you want to try and impress him, that doesn't work.
"He's extraordinary in his sixth-sense ability to spot opportunities and flaws in arguments - and I'd like to think I've got some of those qualities.
"He is very intolerant - as am I - of people who are just show-boating. That's just not how we operate."
He adds: "There are flaws you can't abide in business. You don't want anyone to be dishonest, lazy, uncaring. People look you in the eye and tell you something, it's nice to think they're telling you the truth. Their best might not be good enough but you want people to be straight and honest."
They do have similar qualities, certainly, but unlike Hackney-born Lord Sugar, who quit school aged 16, and has said he is looking for "a complete all-rounder", Littner, a trained accountant, has some polish.
Littner, it's clear, respects education just as much, if not more than experience.
A visiting professor at the University of West London Business School, which was named after him last year in recognition of his business record and backing of the university, Littner, who speaks in crisp clear tones, believes you can study business - it's not something that you simply know, or don't know.
"I'm absolutely sure that you can study business," he says. "There's an enormous value in it. There are lots of skills that are vital to become a good business manager and find your place in the workplace."
"Whatever you study, there's a certain beauty in just gaining knowledge. There's a beauty in learning for learning's sake."
And he brushes away any suggestion that higher tuition fees may discourage students from pursuing higher education. "Nothing is for free," he stresses.
"I don't think it's unreasonable to make it clear to students that, if they want to make it at university, it's a great opportunity to get a job later on that will hopefully propel you to a better salary, but also that it comes with an inevitable price: student debt."
As in previous series, the Apprentice tasks in the new programmes are "old school" - which has attracted criticism. In the first episode aired this week, candidates were told to haggle for fish in Billingsgate Market. Future challenges will see hopefuls sell pet products at The National Pet Show, and become party planners.
Are these skills really integral to British business today, or are they outdated in an era of dotcom billionaires and the mantra of "failing fast"?
"Alan is looking for someone who has old-fashioned skills and the skills that are required in today's and tomorrow's world," says Littner, defending the format. "You can't just say: 'It's all about apps'.
"What you're trying to discover with these apprentices, is their ability to sell, buy, negotiate and show intuition.
"There's no doubt in today's economy, that apps and social networking are important. But it's also about getting on with other members of the team, which is important no matter what business you are in."
And, in the same vein, he insists that The Apprentice is as relevant and entertaining as when it was first launched.
"I don't think it's lost any of its relevance at all," he insists. "Firstly, it's a very informative business programme; it shows what is required to succeed. And then, from the other point of view it's of course hugely entertaining.
"If you listen to Alan Sugar carefully in the programme, the bits of advice he gives in the boardroom are priceless."
But with the show now in its eleventh series, it's possible that Lord Sugar, 68, may one day want to pack it in. Would Littner be game for the job?
"The prospect of following in his footsteps is unthinkable; he's made the role his own. If and when he does decide he's had enough, I think the show would struggle to find somebody of his calibre."
For the moment, Littner is fully committed to the show. He admits that it's been "hard" juggling his work commitments with advising Lord Sugar on TV, but he has been very willing to participate - like his colleague Baroness Karren Brady, who, he says, has a lot more on her plate.
And Littner has been taking some advice himself. He admits that Baroness Brady, who joined as an adviser in 2009, has "shown me the ropes.
"She knows the time to be quiet. I haven't completely mustered that skill," he laughs, adding: "Karren has a woman's view of things.
"She's particularly focused on women; making sure that women have an equal say and an equal right.
"This is something of a mission for her, whereas I don't give it consideration. It makes no difference to me whether it's a man or a woman.
"I think she has something of a bias and I don't blame her - I've got no problem with that. She just feels that she wants to promote women's interests."
While proud of his Jewish roots, Littner, a member of Golders Green synagogue, and supporter of many Jewish and Israeli charities, does not believe that there is anything that makes a Jewish businessman or woman particularly successful.
"I think you see all sorts of people from all walks of life who just break through," he says. "The Jewish community has got a work ethic, but so have the Chinese, Indian and the English."
