Well, I asked a fellow session player tonight. He is a microbiologist who has experience with commercial brewing processes, and is also a keen home brewer as well as one for a good "nose" for a pint he likes.

I'd say to my surprise, he does come down in favour of the steralising/filtering or whatever processes and does think there is a certain amount of myth about the real ales.

One thing he did stress though is if you are really talking about an ale with live yeast, you need a good cellarman - a point raised by others. That, in line with what someone else indicated, adverse processes start happening, etc.

Sorry it's all a bit vague but when this person gets going on a conversation, it can take me a week or more for bits to sink in.

For now, I'm just reporting back and saying perhaps it is not all quite as cut and dried as at least I thought...