Donaldson, 63, is on trial at Newry Crown Court accused of rape and several counts of gross indecency and of indecent assault.

The ex-MP has pleaded not guilty to the 18 alleged offences.

The charges span a time period between 1985 and 2008 involving two alleged victims.

Donaldson’s wife, Eleanor Donaldson – from Dublinhill Road, Dromore, Co Down, denies several charges of aiding and abetting her husband’s alleged offending.

She is facing a trial of the facts after Judge Paul Ramsey ruled her unfit to stand trial on mental health grounds.

The trial of the facts will test the evidence in the case, but cannot result in a criminal conviction.

The first witness in the trial, known as Complainant A, was asked questions by prosecuting barrister Rosemary Walsh KC on Thursday.

The complainant was not in the courtroom, but appeared via a videolink.

Ms Walsh read out a letter which Complainant A said had been written to her by Jeffrey Donaldson in June 2020.

In the letter, Donaldson expressed “how much I truly regret all the hurt, pain and distressed I have caused”.

The letter said he took “full responsibility for it all” and had sought help from God.

The jury heard he described himself in the letter as a “sinner” and had failed to address his “sinful nature for far too many years”.

The letter continued: “I will regret this to my dying day...I understand how deep the wounds are caused by my sinful and selfish actions.” The letter described a “dark situation”.

Ms Walsh asked Complainant A what she believed the letter to be about.

She responded: “I felt he was trying to apologise for perhaps the abuse which had occurred, but he didn’t want to say that formally in writing.

“It felt like an apology letter and it felt like it was written with a lot of guilt.” Evidence in the trial began earlier with the video of a police interview with Complainant A from March 2024, weeks before the Donaldsons were arrested, being played to the jury of seven men and five women.

Donaldson, wearing a dark grey suit, sat in the dock between two court staff as the video was played.

In the interview, the complainant said she had been of primary school age when Donaldson was “physical” with her.

She recalled waking up in the middle of the night on several occasions with a sexual feeling.

She said she later started to have nightmares about “adult men doing horrible things to children”.

She said from primary school age, Donaldson had put his hand up her top – and this “happened for quite a while”.

In her interview, she said Donaldson made comments about the size of her breasts as she got older.

She said she remembered a “significant event” when she was a young teenager when Donaldson “perched” over the top of her, holding a light and had looked at her “private parts”.

She said: “I couldn’t move initially because I didn’t know what had happened.” She said on another occasion Donaldson kissed her and put his tongue in her mouth.

She said this and similar incidents were “very much laughed off as a joke”.

Complainant A said when she was in her 20s, she understood that the behaviour she claimed had taken place was “not normal”.

She said: “I became very angry.” She said she had “watched him in a public role, getting accolade after accolade”.

In the interview, she was asked by a police officer about her earliest memory of waking up in the middle of the night.

She said: “I felt very dirty for a long time.” She added: “It feels black, there is darkness around it, it is black in my head.” The trial, which is expected to last between three and four weeks, continues.

Jeffrey Donaldson, a former long-standing MP for Lagan Valley, was arrested and charged at the end of March 2024.

He resigned as DUP leader and was suspended from the party after the allegations emerged.

Weeks before his arrest, he had led the DUP back into devolved government at Stormont after a two-year boycott of the powersharing institutions.