Sir Jeffrey Donaldson has been convicted of 18 counts of sex abuse, including one count of rape, which he committed against two women when they were children.
The 63-year-old former Democratic Unionist Party (DUP) leader showed no emotion and sat in the dock with his hands clasped as the verdicts were read out at Newry Crown Court on Monday.
His wife Lady Eleanor Donaldson had faced a trial of the facts on mental health grounds, meaning the jury was asked to find out if she did the acts or did not do the acts of which she was accused.
They found that she had done the acts in relation to all five charges – including four counts of aiding and abetting her husband's offending.
The jury of seven men and five women deliberated for 10 hours over three days before coming to their verdicts.
Warning: This article contains distressing information
Donaldson, dressed in a dark blue suit, white shirt and pink tie, was in the dock at the back of Court One, between two custody officers.
He was asked to stand for the verdicts.
As he was found guilty of each charge, he showed no signs of emotion and stared straight ahead.
Judge Paul Ramsey then remanded Donaldson in custody, telling court officers to "take Mr Donaldson down".
Donaldson, who is due to be sentenced in September, was told it would be a lengthy one.
He was then taken from Newry Crown Court in the back of a prison van.
There were two victims in this case and they were referred to as Complainants A and B.
Complainant A is the younger of the two women who Donaldson sexually abused as children.
He was found guilty of eight offences against her, which occurred between 1999 and 2008.
In her interviews with the Police Service of Northern Ireland. which were played in court, Complainant A described a number of encounters with Donaldson including a kiss in which she said he put his tongue in her mouth.
She also said he had put his hands under her bra and rubbed her breasts.
In another encounter, the court heard he used a bright light, possibly a torch, to look at her private parts, an experience that she said made her feel "really frightened".
Complainant A also said his wife Eleanor Donaldson had witnessed the incident when he had rubbed her chest with his hand under her clothing, but did not intervene.
The 10 remaining offences, including the one count of rape, related to Complainant B and were committed between 1985 and 1991.
Like Complainant A, Complainant B took to the stand during the trial and the court also heard an interview she gave to police.
During it she said Donaldson put his hand down her underwear "quite a lot" and detailed the rape.
The court heard of another incident in which Donaldson "lifted her top up and her bra and started to touch her exposed breasts".
Complainant B also said Eleanor Donaldson witnessed an incident in which her husband had "played" with her breasts, but walked away.
Speaking after the conviction Gavin Robinson, the current DUP leader who took over after Donaldson's arrest, said his crimes were "evil" and "heinous" and that he should be stripped of his knighthood and membership of the Privy Council.
Robinson said today was a day for the victims who had bravely spoken up.
He said what they had been put through by Donaldson's denials was "wicked".
"The impact on the victims of having to come forward and to be forced by their perpetrator's denials to give evidence in all the circumstances was cruel in the extreme," he added.
He added it was now clear beyond doubt that Donaldson had abused various positions of power since 1985 and had tried to cover up his vile and manipulative behaviour.
Robinson said neither he nor any of his colleagues had been aware of the allegations faced by Donaldson and their shock reflected that felt by wider society when they were first revealed.
He said the party had acted decisively when Donaldson had been arrested and suspended him.
Geraldine Hanna, Northern Ireland's victims of crime commissioner, said her thoughts are with the victims, particularly as the case took two years to go through the criminal justice system and was under intense media scrutiny.
"So, I really commend the victims in this case for their courage and their fortitude," she told Evening Extra.
Adding that delays in court cases prolong trauma, she said efforts need to be made to improve that: "So that when victims and survivors come forward to report that they're able to get justice and have their case adjudicated as swiftly and as effectively as possible."
The NSPCC in Northern Ireland said it is vital that abuse victims feel they can speak out.
"The victims in this case, now adults, have shown immense courage in coming forward and giving evidence after decades of living with the impact of Jeffrey Donaldson's abuse," a spokesperson said.
Nexus NI, a charity and support organisation dedicated to helping individuals impacted by sexual abuse and abusive relationships, also praised the complainants.
The charity's CEO Joanne Barnes said it is important to praise their bravery for engaging with the criminal justice process "despite the significant personal cost" it can bring.
"We know that the journey through the justice system can test even the strongest resolve," she added.
