In reply to Toreador: I was going to have another little rant about these daft comments like "it's not rare", "Peregrines nest in cities" etc, but I checked the legal stuff a little first re this particular ban.
It is a criminal offence to "intentionally or recklessly disturb any wild bird listed on Schedule 1 while it is nest building, or at a nest containing eggs or young, or disturb the dependent young of such a bird." (RSPB Site)
Ravens aren't Schedule 1 birds, so disturbance isn't an offence.
However, I'm certain that good relations with the RSPB are VERY important, as they have a huge amount of clout when legislation is being drawn up. And we're doing pretty well so far.