The Shakespeare's Globe website has a fascinating interview with Billy Boyd about the relationship between Banquo and Macbeth, and how he and Joseph subtly change the dynamics during different performances. Read it in full on the website.

PB: How is your character changing and developing, if he is at all?

BB: He is! At the moment, there’s a sort of spectrum of where he sits in each scene and how that colours... And I find by the scene that starts with “Thou hast it now: king, Cawdor, Glamis,” you know, when Banquo says that Macbeth has everything that the weird women... that scene is the one that’s most different every night. And I think that’s all coloured by how Joe [Joseph Millson, Macbeth] and myself play the friendship up to that point. So, sometimes it’s very dark. I find myself being very dark with Joe, playing a sort of power game like “I know what you’ve done and just remember that I know.” And there’s a kind of real dark Banquo then. Or, sometimes we’re being really friendly for some reason. And it’s not a choice. It’s just things that happen with me and Joe that night that will mean that there’s more of a friendship up to that point. Then that scene, his point’s more like “look I know you’ve done it and I’m with you on this and I’ll support you.” So, the difference in that scene is the one that really throws me sometimes. And it’s not a choice.

PB: It’s just the culmination of all the things that happen.

BB: To that point, yeah. It just has to get played one way, you know?

PB: Yeah. I guess it’s quite nice to have that kind of flexibility. You get so involved and things just happen.

BB: It is! It’s great! Except sometimes. Like one time we played it really friendly and all the moments clicked and I loved how that scene went. But you can’t be grasping for that because you’ll never get it. Or it wouldn’t make any sense to what’s went before. So, as you see, it is nice but the other side to that is...