Charles Colson: Nixon's right-hand man who served time for the Watergate scandal

He was delighted when a leaked memo said he would ‘walk over his grandmother’ to get Nixon back in

Colson arrives at a Washington courthouse in 1974 to be sentenced for obstruction of justice (AP)

The problem with Charles Colson was, which Charles Colson? The second version, the prison reformer and born-again evangelical Christian leader? Or Colson the White House aide who positively relished his role as President Nixon's tough guy, and was convicted and jailed for crimes arising from that compendium of political wrongdoing known as the Watergate scandal?

Religion certainly never featured greatly in his childhood. The son of a Boston lawyer, he caught the political bug early, working as a 17-year-old volunteer on the 1948 re-election effort of Robert Bradford, Massachusett's Republican governor. Bradford lost but Colson, as he later wrote, learnt "all the tricks" of the underhand campaign – from planting fake news stories to spying on the opposition and getting dead people, so-called 'voting tombstones,' on the ballot.

His big break came in 1956, when he went to Washington as a staffer for the state's Republican Senator Leverett Saltonstall. There Colson met Richard Nixon, then Eisenhower's vice-president, and the two instantly clicked. Colson was devastated when Nixon lost to John F Kennedy in 1960. Eight years later however, Nixon's luck turned. After working on the campaign, Colson moved to the White House, with the title of special counsel to the President.

The affinity between the two was extraordinary and lifelong, to the point that some believed Nixon regarded Colson as the son he never had. What is certain is that each played to the other's base instincts – Colson to his boss's vindictiveness and paranoia, the President to his aide's ruthless devotion to the cause. Even Bob Haldeman, Nixon's redoubtable chief of staff, resented Colson, accusing him of "always doing things behind my back."

Perhaps it was as well. Colson's brief, as the in-house master of dirty tricks, was not for the faint-hearted. He was enabler and enforcer, the man who got things done. He was delighted when the press obtained an internal White House memo of 1972, in which he declared he would "walk over his grandmother" to make sure Nixon was re-elected. Colson compiled Nixon's famous "enemies list" of political and media foes. And fatefully, he hired the former CIA officer E Howard Hunt to head a new White House special operations unit, aka "the plumbers", to stop leaks from the administration.

It was, of course, the break-in at Democratic party headquarters in Washington on the night of 17 June 1972 that led to the scandal that forced the president to resign. Colson himself, however, was in fact brought down not by Watergate itself, but by the plumbers' operation against Daniel Ellsberg the previous year.

Ellsberg, a military analyst, had been quickly identified as the probable leaker of the Pentagon Papers, a classified history of the Vietnam war whose publication in June 1971 by The New York Times outraged the President. Nixon ordered that Ellsberg be discredited. "Get Colson in," he instructed Haldeman, "he's the best, it's the Colson type of man you need."

The Ellsberg case was the plumbers' debut, but ended in disaster when it emerged in early 1973 that Hunt's team had illegally broken into the office of Ellsberg's psychiatrist. By then the noose of Watergate proper was closing around Nixon's inner circle. Colson was indicted, but ultimately agreed to plead guilty to obstruction of justice in the Ellsberg affair. Sentenced to one to three years in jail, he served seven months at a minimum security federal prison in Alabama before being released in January 1975.

Well before that, however, Colson had experienced his epiphany. The story goes it came about when he read Mere Christianity by CS Lewis, a copy of which was lent him by a friend as he awaited indictment. Spiritual conversion did not stop Colson taking the fifth during the Watergate trials to avoid testifying against himself, but thereafter he was a man transformed.

Inevitably, he was mocked by the press, who suspected that the embrace of Christianity was a ploy to reduce his sentence. "If Mr Colson can repent of his sins, there just has to be hope for everyone,'' the Boston Globe tartly editorialised. Repent, however, he did.

A year after his release he founded Prison Fellowship Ministries, giving Christian support to inmates and their families, and in 1983 set up the Justice Fellowship group to promote criminal justice reform. Colson's time behind bars helped turn him into a public opponent of the death penalty, and a supporter of alternatives to incarceration for non-violent offenders. "I deserved it," he later said of his prison sentence; it had been "a great blessing".

Over the last 35 years of his life,Colson wrote or co-authored dozens of books that sold millions of copies,starting with Born Again: What Really Happened to the White House Hatchet Man, published in 1976 and turned into a movie. The royalties went to his prison ministry, as did the $1mTempleton prize, awarded annually to the person who has done most to advance the cause of religion, which Colson won in 1993.

Long before the end his rehabilitation, in religious and Republican circles at least, was complete. In 1998 he met Pope John Paul II. Two years later, his civil rights were restored by Governor Jeb Bush of Florida, where Colson was a resident at the time, and in 2008 George W Bush awarded him the Presidential Citizens' Medal, the country's second highest civilian honour. By then he was an important figure in the influential evangelical wing of the Republican party, pushing for faith-based government.

Democrats and others will, however, most remember him for his role in Watergate, and Colson would not begrudge them. "God used that experience to raise up a ministry that is reaching hundreds of thousands of people,'' he once said. "So I'm probably one of the few guys around that's saying, 'I'm glad for Watergate.'"

Charles Wendell Colson, US government official: born Boston, Massachusetts 16 October 1931; Special Counsel to President Nixon 1969-73; Founder, Prison Fellowship Ministries 1976; married 1953 Nancy Billings (marriage dissolved; two daughters, one son), 1964 Patricia Hughes; died Fairfax, Virginia 21 April 2012.