The 'dont knows' peaked at nearly 40%, fell to 12%, now nearly 30%.
Looking at the graph, 'dont knows' have always been high, 12% looks unusually low.
Conservatives have polled low consistently- even when they have won elections. Around 15% in 2010, down to nearer 10%, now just under 15%.
Labour peaked at 45% on two occasions, always the most popular party, even when they didnt win elections.
Labours popularity has fallen suddenly, and for the first time isnt the most popular party on the survey.