From outcast to the Hollywood red carpet treatment – that is The Sunday Times chief sports writer David Walsh’s remarkable journey in his exposé of drugs cheat cyclist Lance Armstrong.

To mark the release of feature film The Program, charting the rise and fall of seven-time Tour de France winner Armstrong, Walsh was in conversation with The Sunday Times film critic Camilla Long in an @News event on level 14 on Tuesday 20 October.

Over 13 years of relentless pursuit, Walsh was finally able to prove in 2012 that Texan Armstrong was a fraud and the rider was stripped of all his titles.

Walsh told the News UK audience of his transformation from “outcast to dogged journalist” in the perception of his role in Armstrong’s downfall.

As for the red carpet life and top actor Chris O’Dowd playing him in the film, Walsh joked: “I’m 5’6” and Chris is 6’3”, but he’s got an Irish accent!”

He added: “I never felt out of the loop in the making of the film. I saw every version of the film and I was asked my opinion each step of the way. I was blown away by the whole thing.”

Had cycling cleaned up its act regarding drug abuse? Walsh replied: “A lot of improvements in cycling have been made. It’s more serious about testing.”

Describing Armstrong as “an incredible bully,” Walsh was asked if he still thought about the disgraced rider. “I think more about sex than Lance Armstrong!” he quipped.