Lister: Put simply, by killing us they killed themselves, because once we were dead it was impossible for us to become them in the future, and return in time to kill ourselves in the past, even though it was the present.

More from Red Dwarf Series VII

• Cat: Yeah, it’s awful, man, when a woman screws you up so bad you want to become a squirrel.
• Kristine Kochanski: I don't know about this. I've never been seduced by Predeterminism Theory before.
• Kryten: I’m up and down more often than a pair of kangaroos in the mating season!
• Kryten: My goodness. I do believe I'm drunk. I suddenly feel the need... to strut my funky stuff!
• Lister: I prefer something slightly more melodious. Like the long, drawn-out death rattle of a man suffering from terminal flatulence.
• Rimmer: Ace and Skipper?! You sound like a kids' TV series about a boy and his bush kangaroo!