Chancellor George Osborne and ex-prime minister Gordon Brown will today appear before the Leveson Inquiry as the investigation into media standards enters its most politically-charged week.
With David Cameron due to give evidence on Thursday, both the Conservative and Labour leaderships will face searching scrutiny over their relationships with the big media barons.
Much of the questioning of Mr Osborne is likely to centre on his role in building relations between the Tory leadership and Rupert Murdoch's News Corp empire in the periods before and after the 2010 general election.
In opposition, he played a key role in recruiting former News of the World editor Andy Coulson as the Conservatives' director of communications in 2007.
When he appeared last month, Mr Coulson said that within two months of his resignation from the paper in the wake of the phone-hacking scandal, Mr Osborne had begun courting him to work for the Tories.
The Chancellor may also face questions over any role he played in the saga over News Corp's takeover bid for BSkyB once the Tories were in power.
The inquiry has previously heard that Culture Secretary Jeremy Hunt had texted him expressing concern about the way the issue was handled in government.
When Business Secretary Vince Cable was stripped of his responsibilities for the bid after voicing his hostility to the Murdochs and the issue was was passed to Mr Hunt, Mr Osborne texted back: “I hope you like our solution”.
When he enters the witness box in court 73 at the Royal Courts of Justice, Mr Brown can also expect an examination of his dealings with News Corp and the Murdochs.
Rupert Murdoch told the inquiry that they had previously enjoyed a “warm personal relationship”.
In 2008, Mr Murdoch's wife, Wendi, and then News International chief executive Rebekah Brooks attended a so-called “pyjama party” at Chequers hosted by Mr Brown's wife, Sarah.
However, Mr Murdoch said relations broke down after The Sun switched its support to the Conservatives in the midst of the 2009 Labour Party Conference.
The inquiry is also likely to discuss The Sun's 2006 story disclosing that Mr Brown's son Fraser was suffering from cystic fibrosis.
Mrs Brooks denied the story had been obtained through hacking into medical records and said the information came from a source connected to a charity for the condition.
Also giving evidence to the inquiry this week are former prime minister Sir John Major and Labour's leader and deputy leader, Ed Miliband and Harriet Harman, who appear tomorrow.
They will be followed on Thursday by Deputy Prime Minister Nick Clegg and Scotland's First Minister Alex Salmond.
PA
