Michael McKevitt faces long imprisonment after his conviction for terrorism, but security forces still view his group as a big threat to peace in Northern Ireland.
They regard Mckevitt as a diehard republican who shunned the peace process.
The Special Criminal Court decided McKevitt was a key figure in The Real IRA and not as he portrayed himself - the owner of a popular fish and chip shop in Dundalk.
McKevitt was a senior figure in the IRA - Irish Republican Army - and, for many years, was the organisation's quartermaster, responsible for hiding and transporting its huge and deadly arsenal around Ireland.
His wife Bernadette is the sister of the republican icon Bobby Sands, the first IRA man to die in the hunger strikes of the early 1980s.
However, McKevitt fell out with the mainstream republican movement over its peace strategy and became perhaps the most important figure in the shadowy and dangerous world of dissidents.
Security experts say his downfall was due to his sudden need to start dealing with the tricky business of raising money, when his real expertise lay in handling and hiding weapons.
Implacably opposed to British rule in the province, The Real IRA was formed in November 1997 by disillusioned IRA members.
They broke away from the mainstream movement in protest at the political strategy of the IRA's political wing, Sinn Fein.
They argued negotiations with the British government and Northern Irish protestants would sell the Catholic community short of its goal of an united Ireland.
Less than a year later the group was responsible for the bloodiest single attack in three decades of conflict - when a car bomb in Omagh killed 29 people.
Sinn Fein leader Jerry Adams was
accused of betraying the
Security sources say the group is small, with an active membership in the dozens rather than hundreds.
Its main base is around the Irish north-eastern town of Dundalk, but it has some strength in Belfast, Londonderry and County Donegal.
Most Real IRA attacks have been carried out using homemade explosives.
But the group is estimated to possess a few dozen rifles, machineguns and pistols, a small quantity of Semtex commercial high explosive, and a number of detonators.
The success of the Irish police force in infiltrating the Real IRA has landed many key members in jail, leading some to conclude they were a spent force.
But the past few months has seen an increase in dissident activity, with police in Northern Ireland foiling bomb attacks in Belfast and Londonderry.
The Londonderry device was more than twice the size of the Omagh bomb, and security sources admit it was only a sharp-eyed police officer which stopped it from being used.
The dissident republican movement, and indeed anti-peace process groups, have undoubtedly been dealt a serious blow by McKevitt's conviction on Wednesday.
But security forces say it would be foolhardy to believe the blow is fatal.