Oh I can assure you Hugh CAN sing. Check him out on You Tube. This wasn't his best vocals, but down to using "live vocal takes" so a few of those umpteen takes were probably much better than the one Hooper went with. But he wasn't miscast, nor, the more I watch it and vocal quality a la stage version becomes less and less of an issue, was Russell. I agree with the poster up thread (I think it was Irma Bunt
who said they'd seen and heard Javroche sung better but never better acted.
Again missing the point, I shouldn't need to be looking on YouTube video's to verify that an actor I've just seen in a musical can actually sing!