I could hardly hear David Attenborough's voice on this wonderful programme with my TV. It seemed as tho' he was peaking 2 on the PPM  with the music reaching 5. The music was appropriate -but not at the expense of losing the narration. It was a voice under and not a voice over. Perhaps there was something wrong with my TV?--answer-"no there wasn't"

I didn't have a problem listening to the programme, but was that because I was listening to multi-channel audio HD, where the voice over was centre channel?

Perhaps the encoding to two channel audio wasn't good?

This whole argument regarding Dialogu/Voiceover/Soundtrack audibility continues to be a problem that most broadcast organisations seem unable to address. As an ex Senior Sound Supr. I can only suggest that the mixing is being undertaken in sound laboratory conditions (Dubbing Theatres) which do not have the availability of 7.1/5.1/Stereo/Mono comparison when monitoring. Either that or the dubbing mixers can't be bothered to check. One of the fundamental lessons of BBC sound training right up to the time that quality checking was thrown out the window was that the out of phase content of stereo sound was what gave the audible excitement to the listener. This is even more the case in surround sound, and I would commend the sound mixers of today to hark back to some of the experiences of the past to make sure that complaints like the ones appearing more and more in forums like this and in the press in general diminish in future so that the general public can receive a quality of broadcasting higher than that presently offered.