For decades, audiences have believed a feud between talk show greats David Letterman and Jay Leno began when Letterman lost out on Johnny Carson’s old seat at the Tonight Show.

But Letterman has now attempted to put those rumours to bed, hinting at how his once close relationship with Leno crumbled due to the comic’s insecurities.

And, as he spoke out about the years-long feud in an interview with Oprah Winfrey, Letterman made an unprecedented move complimenting Leno, calling him ‘the funniest person I have ever known’.

‘We were always friends before all of this happened,’ Letterman, 65, said in the Oprah’s New Chapter interview, which airs in full on the Oprah Winfrey Network on January 6.

‘He has a way – he’s an unusual fellow. I’ve never met anyone quite like Jay.

And I will say – and I’m happy to say – that I think he is the funniest guy I’ve ever known. Just flat out, if you go to see him do his night club act, just the funniest, the smartest, a wonderful observationist and very appealing as a comic.

‘Therefore, the fact that he is maybe the most insecure person I have ever known… I could never reconcile that.’

The high-publicised feud has previously been blamed on Letterman being passed over as the replacement for Carson in 1992, when Leno was given the job instead.

The battle was so well known that it was made into a 1996 HBO film, The Late Shift.

And this year, the spat hotted up when Leno ended his 17-year reign at the Tonight show to begin the Jay Leno Show for NBC – which failed to garner the ratings of his rival’s show.

Letterman went from strength to strength, overtaking Conan O’Brien in the late-night ratings.

The rivals have managed to laugh at their mutual animosity, appearing in a commercial during the 2010 Super Bowl in which they were separated on a couch by Oprah Winfrey.

Letterman will also address one of the rockier moments of his career in the interview. In October 2009, he plunged to new lows following a bizarre on-air revelation that he had cheated on his wife.

While taping the Late Show, Letterman admitted to the string of affairs with female employees after he became the victim of an $2 million extortion plot from a producer.

He will also talk about how he repaired his relationship with wife Regina Lasko, whom he had only married earlier that year, and his battle with depression.

To see the interview in its entirety, tune in to “Oprah’s Next Chapter” on Jan. 6 at 9 p.m. ET on OWN.

Ashton Tyler | Elite.