McPartlin was more than twice over the legal limit when he smashed into two other cars in south-west London in March 2018. He was driving with his mother in the car, and both cars he hit contained children.
McPartlin was fined £86,000, believed to the largest drink-driving fine ever handed down in the UK. He was also banned from driving for 20 months.
The interview follows ITV’s Chief Executive saying that the network “is not solely dependent on Ant and Dec.”
Dame Carolyn McCall told the Broadcasting Press Guild: “People were very upset about what happened, what Ant did.”
After the crash, McPartlin announced he was immediately withdrawing from his television commitments and going into rehab.
Donnelly said in the interview that he would be lying if he said he had not thought about separating from his on-screen partner of almost 30 years.
However, ultimately, he wanted his partner healthy and happy, and the relationship back to what it was.
McPartlin said: “For the first time in many years, all we talked about were deep things like how we felt, and what the future held, and where we were, and all the chaos that has come along, especially for me.”
The presenters are due to return as a TV duo next Saturday for the first time in a year on the ITV show Britain’s Got Talent.
The full interview will be published in Saturday’s Guardian Weekend magazine, and on theguardian.com this Saturday morning.