Who is Thomas 'Slab' Murphy?

Thomas 'Slab' Murphy arrives for his sentencing hearing in Dublin. He was given 18 months in jail.

This was far from any ordinary, run-of-the-mill tax case.

The man involved had been a high-profile target for the police and other law enforcement agencies on both sides of the border for decades.

Thomas "Slab" Murphy claims he is just a farmer.

But he is also alleged to have been one of the most powerful figures within the Provisional IRA.

It has been claimed the south Armagh man was, at one time, the organisation's overall commander, its chief of staff.

Sinn Féin leaders have said he was a farmer who helped sow the seeds for the peace process.

Speaking after properties belonging to Murphy were raided by police 10 years ago, Sinn Féin president Gerry Adams said: "Tom Murphy is not a criminal. He's a good republican.

"He's also, and very importantly, a key supporter of the Sinn Féin peace strategy and has been for a very long time."

In December last year, Deputy First Minister Martin McGuinness praised him for "his invaluable support" for the peace process.

"What we have achieved in the north of Ireland over the last 20 years has been nothing short of amazing, that's what the world tells us, what you've done here has been amazing," he said.

"Well, the amazing wouldn't have happened without the support of people like Tom Murphy."

Thomas "Slab" Murphy has denied being an IRA leader, but for years police - on both sides of the border - regarded him as one of the organisation's most senior and influential figures.

In 1990, he sued the Sunday Times which had alleged he was an IRA commander, and had directed an IRA bombing campaign in Britain as well as helped to import tonnes of weapons from Libya. He lost the case.

He appealed the ruling, but in 1998 he lost again.

Retired British Army officer Colonel Richard Kemp recently told a BBC Northern Ireland Spotlight programme that he had no doubt Murphy was a senior member of the IRA.

He served several tours of duty in Northern Ireland, and went on to work in intelligence at the Cabinet office.

Col Kemp told the programme that his role gave him access to intelligence information about IRA activities, including lists detailing the identities of the main IRA figures operating in south Armagh.

When asked if Thomas "Slab" Murphy was on the list, he replied: "Thomas Murphy was one of the main people on that list. In fact he was, as we understood it, the head of the Provisional IRA in south Armagh."

Police on both sides of the border also regarded Murphy as the head of a huge multi-million pounds smuggling empire.

His farm in Ballybinaby straddles the border between Northern Ireland and the Republic, which police said allowed him to exploit, and defraud, the tax authorities on both sides.

In 2004, the BBC's Underworld Rich List named him as the wealthiest smuggler in the UK, claiming he had amassed up to £40m through smuggling oil, cigarettes, grain and pigs.

Murphy's conviction for agricultural tax offences marked the culmination of years of work by authorities north and south.

'Untouchable'

He had been under investigation by the police in Northern Ireland and the Republic for years, and came to be viewed as untouchable. Until now.

Like the "untouchable" American gangster Al Capone, tax evasion proved to be his Achilles heel.

Some republicans have also used the Al Capone analogy, but pointed out that he was found guilty by a jury, whereas Murphy was convicted in the Republic's non-jury Special Criminal Court.

Critics have said that would simply not have been possible, because jury members could face intimidation.

That view was endorsed by Northern Ireland's former First Minister Peter Robinson, who said it would have been "sheer madness" for Murphy to be tried in front of a jury.

"I will resist any temptation to make reference to Al Capone and the style of his conviction," he said after Murphy was convicted.

"It is essential to say nobody is above the law and everyone is answerable to the courts."