Obviously Russell is singing this song on the Beat is the Law video, and as usual there's a second vocal. It sounds like Jarvis, but Pete is definitely singing too. Hard to imagine Jarvis being one of those people who can play drums and sing at the same time anyway, so could the assumption that it's J&R singing be wrong...?
Haven't really watched the video in sufficent detail to see what Manners and Jarvis are doing, but it definitely sounds like the latter singing on the recordings.
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"Yes I saw her in the chip shop / so I said get yer top off"
Jason, you had the pleasure of seeing this live? May I ask where? Mark definitely Jarvis on the recording, but Manners is visibly singing on the video. Unfortunately Jarvis' drumming can't be seen, so can't tell if there's a mic or not.