Nick Cave has shared the secrets of his friendship with long-time collaborator Warren Ellis in his latest entry for The Red Hand Files.

• READ MORE: Nick Cave & Warren Ellis live in London: Minimal elements for maximum impact

The pair have worked together across various projects since 1993 including Nick Cave & The Bad Seeds and Grinderman.

After being asked by multiple fans about their friendship and songwriting, Cave shared his theory that there are three levels of friendship: essentially those defined by “a shared experience,” “someone who has your back,” and ones who can “bring the best out in you”.

“None of these levels are mutually exclusive and sometimes you find someone who fulfils all of these categories. If you find a friend like that, hang on to him or her. They are rare,” he explained.

“Warren is such a friend,” he continued. “The reason why we have had such a long and productive artistic collaboration is because these three levels of friendship are firmly in place; we understand the nature of friendship and we look after the friendship itself.”

Cave also said that the pair “do not have to deal with the problems of an unstable relationship, or questions of status, or struggles for power,” adding: “We are friends, pure and simple, and we just get on with the work at hand – two people creating something greater than the sum of its parts – the fruits of the collaboration emerging directly from the friendship itself.”

Yesterday (November 23), Cave and Ellis announced plans to score French documentary La Panthère Des Neiges.

The pair have teamed for the soundtrack, which will be released digitally on December 17 on Invada Records.