John Yates is the senior Metropolitan Police officer leading the "cash for peerages" probe.
John Yates has a track-record of working on high profile cases
BBC News looks at his track record of investigating allegations of high-profile corruption.
Deputy Assistant Commissioner John Yates is no stranger to controversy.
In the 1990s he headed an investigation into internal police
corruption and led the investigation that prompted the successful
bringing of perjury charges against Lord Archer.
More recently, 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 in July last year.
Mr Yates joined the Metropolitan Police in 1981, spending time both in uniform and as a detective.
He went on to lead investigations into more than 20 murders.
The senior policeman worked as Staff Officer to Met Commissioner Paul
Condon during the period of the Macpherson Inquiry into the death of black
teenager Stephen Lawrence between 1999 and 2000.
Six years ago, in an investigation that proved to mark a watershed, Mr Yates led the first corruption inquiry to use the evidence of both a female and detective supergrass.
Then a detective superintendent, he led the inquiry which focused on internal
police corruption in a crime squad based in East Dulwich, London.
The senior policeman established his reputation as a robust operator capable of handling cases in the media spotlight with his involvement in the Archer case, as well as the failed prosecution of royal butler Paul Burrell and the Who Wants to be a Millionaire fraud trial.
He is also at the centre of the row over the shooting of Jean Charles de
Menezes at Stockwell tube station last July.
His evidence to the IPCC could prove crucial in its decision on whether to
criticise Met Commissioner Sir Ian Blair's handling of the police response to
Mr Yates said he was "humbled" by the dignity shown by Mr Menezes' parents after he met them in the town of Gonzaga last year.
Away from investigating corruption, the policeman demonstrated his versatility by leading the British police response to the Boxing Day tsunami.
Lord Levy was arrested as part of the "cash for honours" investigation
He headed Operation Bracknell which opened a bureau to log details of those missing, describing it as an "unprecedented challenge".
Almost 2,600 police officers from across the UK were deployed to help.
Mr Yates' achievements during the tsunami response led to him being awarded the Queen's Police Medal (QPM).
However, the inquiry into whether peerages were offered in return for party donations appears to be Mr Yates' toughest and most sensitive challenge to date.
It follows the revelation earlier this year that multi-million pound loans were secretly given to Labour before the last election.
The investigation led to the arrest of Lord Levy, Labour's chief fundraiser and of Tony Blair's closest allies.
Lord Levy's arrest came two days after it emerged that he allegedly advised curry tycoon Sir Gulam Noon he need not tell a Lords vetting watchdog he had lent Labour £250,000.