Yes Fraggle it is White Men Can't Jump....now we know what brought on that saying....good job Duncan!
When Duncan heard the trio's plans he decided that he just wasn't up for all that cross country running. Seriously though, it's not Duncan's fault he didn't want to get his hair wet! It seems he had an aversion to water, after all, we all know him as the fiery type.
P.S. I do actually believe that he stayed for honour and duty and all that jazz but I find it too much fun taking the mickey out of him.