Sebastian Barry became the first author ever to win two Costa Award book awards, with a gay novel that was inspired by his son’s coming out.

Barry, who last won the Costa for 2008 for The Secret Scripture, has been awarded the £30,000 prize for Days Without End, the story of a love affair between two men during the American Civil War.

Described by the Costa judges as a “miracle of a book”, it follows Sligo boy Thomas McNulty who escapes the Irish famine and joins the US Army. Along the way he meets John Cole, and the two begin a love relationship that will span their lives, in a book that is at once intimate and epic.

Accepting his award, Barry said the win had made him “crazy happy from the top of my head to my toes, in a way that is a little bit improper at 61.”

He also paid tribute once more to his gay son, saying: “This book is dedicated to Toby eternally.”

Barry went on to tell The Telegraph that he wished for a world in which homophobia no longer existed.

“As a father, I’m trying to mobilise the world to stop being in any way prejudiced towards people who are gay, since they are actually incredible instances of human existence and should be revered and emulated rather than in any way feel unhappy. I mean, when somebody is bringing to bear a comment on your 16-year-old son, you’re on action stations.

“He said a beautiful thing to me after he’d read the book: ‘You’re not gay, dad, but you’re an ally.'”