Not only did the Lib Dems win, but there was a swing of 24,000 votes, a 16,000 majority turned into an 8,000 defeat. To which should be added a drop in the vote from 76% of the electorate to 52%. So many Conservative voters showed their disenchantment by just not voting at all.
It is, almost certainly, as Kim suggests a reaction to current discontent, but my goodness, what a reaction, to see a 16,000 majority turned into an 8,000 loss, plus all the abstainers, isn't just a slap on the wrist, it is a really hard kick where it really really hurts.
Factors in the swing included HS2 and the new planning regulations, or rather plans for a lack of regulation.