Profile this week is Facebook co-founder and Chief Executive, Mark Zuckerberg. With new investment by Goldman Sachs, the company is now valued at 50 billion dollars. But how much do we know about the man behind it all? Is he really the character portrayed in recent film, The Social Network? And what next for the 26-year-old now thought to be the world's youngest billionaire?

The royal wedding this year will bring Prince William back to Westminster Abbey, the place where he first attracted global attention as the son mourning his mother's tragic death. Since then he has had to negotiate his relations with the Spencer and Windsor families, and follow the carefully constructed training of the man likely to be king. His time as a student, professional and military careers have all been steps on this path. So how difficult an inheritance has this been? And what does the preparation of William the young prince tell us about plans for the future role and image of the monarchy?

In this week's Profile, Chris Bowlby considers the mix of family duty, personal choice and careful PR that has gone into the making of Prince William.

Producer: Daniel Tetlow.

The numbers are staggering: more than 1 billion music video online hits, record sales of more than 50 million, number 7 on the Forbes List of the world's 100 most influential women. Not bad at all for 24 year old Stefani Germanotta, a girl from New York's Lower East Side whom the world now knows as Lady Gaga. In this week's Christmas day Profile, Stephen Smith follows Germanotta's story from rebellious, classically trained pianist to pop's newest and hottest icon.

Glenn Beck, the provocative tv and radio talk show host, represents the polarised politics of American media. Those who like him describe him as an 'inspiration' and those that don't call him 'toxic'. His TV show on Fox News averages a daily audience of two million viewers.

Beck doesn't shy away from controversy, recently describing progressivism as "the cancer in America eating our Constitution" and referring to President Obama as having "a deep-seated hatred for white people or the white culture". Along with Sarah Palin, he's often invoked as a spiritual leader by the Tea Party Movement

Mary Ann Sieghart looks at the man who grew up in small town America as a Catholic, became a disc jockey in his home town of Mount Vernon at the age of 13, converted to mormonism and now runs a multimedia empire.

Mary Ann Sieghart profiles Iain Duncan Smith whose Work and Pensions Department will be hit during next week's Spending Review. His proposed welfare reforms have been described as 'the biggest since the war-time work of Beveridge' and a white paper is expected after the Spending Review.

Iain Duncan Smith started out briefly in industry after leaving the army where he served twice in Northern Ireland. His father was a famous World War II flying ace & his mother a ballerina.

In the 1990s, he was best-known as one of the Tory party's most strident euro-sceptic MPs. His short two year leadership of the Conservative party was mostly unsuccessful. The "quiet man" was unable to unite his party. But it was during this time that Iain Duncan Smith began to see the need for welfare reform. After he was ousted from the leadership he set up the Centre for Social Justice and is credited with forming much of David Cameron's social agenda.

Mary Ann Sieghart talks to his political allies & foes, long-standing friends and the people who began to change his political direction.

Producer : Rosamund Jones.

For this week's BBC Radio 4 Profile, Mary Ann Sieghart focuses on Yvette Cooper, recently announced as the new Shadow Foreign Secretary.

Yvette Cooper became an MP in 1997 and became politically close to Gordon Brown. She's held a number of Ministerial roles, introducing sometimes controversial legislation and facing controversy herself during the MPs' expenses investigation. She has juggled high profile jobs with bringing up three young children and she won this week's shadow cabinet elections - by a large margin.

So how did Yvette Cooper manage to become so popular so quickly? And with this latest promotion, where might her political future take her in Ed Miliband's new Labour Party?

Brazilians go to the polls this weekend, to elect a new president, replacing the charismatic Lula da Silva. And, with Dilma Rousseff far ahead in the polls, it looks like the country could get its first female leader. It's been an amazing journey for Rousseff, the daughter of a Bulgarian immigrant. In the 1960's, she joined a revolutionary urban guerrilla group after the military coup, and was imprisoned and tortured.

Eric Daniels, CEO of Lloyds Banking Group, Britain's biggest retail bank, who announced this week that he will retire in 12 months with an estimated £13 million pay off package. He's the last survivor of the big banking beasts - Fred "the Shred" Goodwin and co - who were at the helm when the banking crisis struck. Daniels is still being pursued by angry shareholders who saw their stake plummet after he presided over the Lloyds takeover of HBOS.

A heavy smoking, cricket-loving American, of Chinese/German parentage, Eric Daniels won a reputation as the quiet man, a safe pair of hands, risk averse: the archetypal boring banker. That was before Gordon Brown persuaded him and his chairman at Lloyds to take on HBOS at the height of the banking crisis. Triumph rapidly turned to disaster. As the Independent Banking Commission this week reveals its plans to re-shape the banking sector, Morland Sanders profiles a respected City figure, and through Daniels' story, throws a revealing light on Britain's recent banking culture and crisis.

Producer: Andy Denwood

Jonathan Maitland profiles Danny Alexander, Chief Secretary to the Treasury in the coalition government and Liberal Democrat who will wield the axe as the UK enters a new age of austerity. Alexander emerged from a background in communications and a short career as a politician --he was first elected to a Highlands seat in 2005 --to become Treasury Chief Secretary. It is a post that many commentators say makes Danny Alexander the third most powerful man in government, after the Prime Minister and the Chancellor of the Exchequer and ahead of his own boss the Deputy Prime Minister. So how did a man whose last job outside of politics was to run communications for the Cairngorms National Park get so far so fast? And how will he fare once the cuts he is overseeing begin to take hold? Jonathan Maitland talks to his family, his friends and political commentators about the MP from Inverness, Nairn, Badenoch & Strathspey.

John Yates, the Assistant Commissioner at the centre of the storm about the Metropolitan Police's investigation into celebrity phone hacking at the News of the World, under the editorship of Andy Coulson, now the Prime Minister's chief spin doctor. Yates is a high flyer and no stranger to high profile and controversial cases. He led the perjury case against Lord Archer, the 'cash for honours' investigation, was involved in the Stephen Lawrence enquiry. In 2005 he travelled to Brazil to meet the parents of Jean Charles de Menezes, who was shot dead by police after being mistaken for a suicide bomber, and with an offer of financial compensation from the Met. Yates is also responsible for counter-terrorism. Yates is in the spotlight again this week as MPs questioned his judgement about the limits of the hacking enquiry and the closeness of the Met's relationship with News International. Yates has now agreed that new evidence means the investigation will be re-opened. Colleagues and critics talk John Yates, the man tipped to be the next Commissioner of Scotland Yard, as he faces enormous pressure from all sides.

Producer: Samantha Fenwick