Mark Felt, aka Deep Throat, and the Watergate scandal

An exterior view of the Watergate complex in Washington, DC. In June 1972, the headquarters of the Democratic National Committee, based in one of the Watergate's office buildings, was broken into and bugged by men subsequently linked to White House efforts to re-elect Richard Nixon. It was the investigation of this burglary that led to the unravelling of Nixon's presidency Photograph: Hulton Archive/Getty Images

Richard Nixon, the only US president ever to resign the office. As the scandal unfolded, his role in a cover-up, in particular the authorisation of hush money to one of the burglars, saw him quit in August 1974 before facing impeachment or conviction. He died in 1994, aged 81 Photograph: David Hume Kennerly/Getty Images

Felt (right) with his wife and the FBI director J. Edgar Hoover, following the presentation of his 25-year service award. The FBI number two during the Watergate period, Felt first met Bob Woodward when the future Washington Post reporter was a navy lieutenant, eager for career advice, delivering classified documents to the White House Photograph: /Rex Features

Bob Woodward (left) and Carl Bernstein, the Washington Post reporters who investigated the case, seen at their desk in 1973 Photograph: Bettmann/Corbis

Robert Redford and Dustin Hoffman as Woodward and Bernstein in the 1976 film All The President's Men, based on the reporters' own account of the investigation Photograph: The Kobal Collection

Gordon Liddy, the chief operative of Nixon's infamous 'plumbers' unit (set up to investigate leaks) and the mastermind, with Howard Hunt, of the Watergate burglary. He was sentenced to 20 years in prison for conspiracy, burglary and illegal wiretapping, later commuted to eight years by Jimmy Carter Photograph: Corbis

Charles Colson, the special counsel to Nixon, was a man with a reputation for ruthlessness and a member of the White House re-election committee linked to the burglary. He was indicted for his role in the conspiracy and served seven months in jail for obstruction of justice, insisting he was innocent of all other charges Photograph: Neil Selkirk/Time & Life Pictures/Getty Image

Judge John Sirica with the seven men charged with involvement in the Watergate affair. From left: John Ehrlichman, former presidential aide; HR Halderman, former White House chief of staff; Gordon Strachan, former aide to Halderman; Kenneth Parkinson, a lawyer retained by the committee to re-elect Nixon; Colson; former US attorney general John Mitchell; and Robert Marcian, the former head of internal security at the US justice department Photograph: Frieda Reiter/ ABC/Associated Press

The tapes that furnished definitive proof of Nixon's role in the scandal - and also of his frequent swearing - are listened to by US Representatives
Listen to the Nixon Watergate tapes Photograph: Hulton Archive/Getty Images

The scandal shocked the US. This cartoon of Nixon, by Ralph Steadman, appeared on the cover of the September 1973 Rolling Stone, which featured a piece by Hunter S Thompson Photograph: Rolling Stone

From the film version, Redford plays Woodward talking to Deep Throat in All the President's Men Photograph: Ronald Grant Archive

Felt shows off his pistol skills in 1958. He revealed himself to be Deep Throat (speculation on the source's identity had extended to the former US president George Bush) in 2005
After 33 years, Deep Throat, the man who brought down Nixon, confesses all Photograph: Howard Moore/AP

Richard Nixon resigns the presidency at the White House with his family in 1974. Photograph: Keystone/Getty Images

Nixon smiles and gives the victory sign as he boards the White House helicopter for the last time Photograph: Bettmann/Corbis

Ben Bradlee, the Washington Post editor through the Watergate investigation, Bernstein (left) and Woodward in 2005. Woodward and Bernstein are both now political authors Photograph: Katherine Frey/AP