Loyalist paramilitary Michael Stone has denied trying to kill the Sinn Fein leadership.
He said the day he tried to force his way into Stormont was simply "an act of performance art".
The 53-year-old burst into Parliament Buildings allegedly carrying explosives and a replica gun in November 2006.
Stone faces 13 charges at Belfast Crown Court, all of which he denies, including trying to kill Gerry Adams and Martin McGuinness.
Stone was speaking as he began giving evidence in his trial.
Rather than trying to wreck the peace process, Stone said he had been trying to help the peace process by staging an art-based protest at the political deadlock that existed at the time.
I'm destroying the iconography of Michael Stone, loyalist hero
The convicted triple murderer was released early under the terms of the Good Friday Agreement.
He had been jailed for life for a 1988 gun and grenade attack on the republican funeral of three IRA members shot dead by the SAS in Gibraltar.
Stone told the court his actions were intended to "put a proverbial rocket up the backsides" of the politicians.
"I'm destroying the iconography of Michael Stone, loyalist hero," he said.
"It's a comic parody of my former self. I would rather be remembered as an eccentric artist that got it wrong in performance art than for my past, when I did some terrible things."
He told defence QC Orlando Pownall he did not intend to harm anyone, let alone Mr McGuinness, as "he would be the last man I would target because he was a security force asset".
Each item he was carrying had symbolic significance, he said, including a bird-shaped pair of scissors as a "begrudging" symbol of Irish republicanism rising from the flames, and a poppy badge on his jacket as a mark of respect for "fallen comrades".
He said a sponge inside the butt of the fake gun was to symbolise the "sponging unionists", the wire he had with him was for the "precarious path to peace and reconciliation," harking back to a painting he gave to Archbishop Desmond Tutu.
Stone told the court he tried to keep everything in a "monochrome pallet" - black, white or grey.
"The symbolism of that was as in life, not everything is black and white - my perceived attack is a grey area, that it was an attack of art, an artistic protest," he said.
Even his clothing had its own symbolism, he said, including a pair of sunglasses, in that he had worn the same outfit in 1974 to a mass protest against the Sunningdale Agreement.
He said he wore a fisherman's hat because Martin McGuinness's alleged codename in the security forces was "the fisherman".
"It was symbolic that had I been some sort of fanatical loyalist that McGuinness would have been the last man I targeted because he was a security force asset," claimed Stone.
Asked if there would have been any symbolism if the flight bag had ignited, Stone said "no, there would not have been".
The court was shown Stone's impression of how his graffiti would have looked
He said that before travelling to Stormont, he dyed his hair and goatee beard so he would not look "overweight and grey-haired" in front of the world's media and press gathered for the day's events.
Stone said he was a "very political person" who "fully supported" the peace process and devolution but was anxious about the political vacuum being caused by Sinn Fein and the DUP, fearing the impasse could cause a "return to the bad old days".
He said he had planned to do something "perhaps a year and a half" before 24 November 2006 but only came up with the plan of "performance art work" around six weeks in advance.
He claimed his plan was to daub political graffiti on the walls of the building, to leave the nail bombs, which he called "props," at the base of each column and to use the "flash bang" device inside the flight bag to "clear the building".
Asked by his defence lawyer if he had intended to hurt or injure anyone, Stone replied "no".
When asked what he had hoped to achieve in the days after the incident, he said he wanted the politicians to ask "why?"
"Why has a man that signed up to to the Anglo-Irish, sorry, Good Friday Agreement, that when released for a year, promoted peace, why has he suddenly done the opposite?" he told the court.
The court was shown a large oil painting where Stone gave an impression of what his protest graffiti would have looked like had he not been disturbed by security staff.
He said the top of the painting was made to look like a circus tent as Stormont had previously been described as "a circus".
Stone is due to be cross-examined by the prosecution on Tuesday.
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