Roy Keane has admitted he is not sure whether he will ever forgive former Manchester United manager Sir Alex Ferguson after his explosive departure from Old Trafford.

Speaking at the launch of his new book The Second Half at the Aviva Stadium in Dublin on Thursday, the former United captain pulled no punches when asked whether his relationship with his old manager will ever recover.

“Not sure, not sure. Football is a small world, you will cross paths with people again,” Keane responded when asked if he could ever forgive Ferguson.

“The problem I had, is that when you hope you have known someone for some time, it’s afterwards when people start coming out with all sorts of nonsense. When you think what he made out of it, millions of pounds, statues. But to criticise people who have earned him success … would I forgive him? I don’t know.

“If we cross paths. I’m sure we will … cross paths, that is. Lots of stuff I let go, but eventually you have to go, enough is enough. You have to defend yourself.”

Keane was also asked to elaborate on why he fell out with Ferguson and made reference to the controversial interview with in-house TV station MUTV which eventually led to his departure. “It is quite hard to explain. You just knew,” he said. “There was a lot of propaganda from United about this leaked video that shouldn’t have been played. United were quite happy to let that run. I had to fight my corner on that one. No one had an issue with that in terms of the players, it was just Ferguson and [assistant coach Carlos] Queiroz.

“Sometimes you just know these things. Just the way it was handled. Ferguson has pals in the media, I can spot them a mile off, some of them are here today. I can see them, putting out little snippets, lies.”

Now the assistant manager of Aston Villa and the Republic of Ireland, Keane is in Dublin to help Martin O’Neill’s side prepare for the Euro 2016 qualifier against Gibraltar on Saturday. He admitted the book release had been a slight distraction from his usual duties but revealed his motivation for releasing it was “to defend himself against stuff which was untrue”.

“I had no real plans to write a book. I had plenty of offers these last few years, particularly when people were telling a pack of lies about me these last few years,” he said. “But the stuff I have gone into is me defending myself against stuff I felt was untrue.

“There was also a lot of good stuff, really good stuff. This idea with me falling out with everybody … People will look at the negatives.”