Why have UK citizens become disillusioned with politicians and politics in general since the 1940s?

There are two main explanations for this trend:

The 'Demand Side' explanation suggests that people are less engaged with politics because of the citizens themselves; in other words it is not the fault of political institutions or politicians but simply the fact that most people have very little experience of politics and tend to judge politicians from afar with naive aspirations about what is possible. A potential solution for this is better citizenship education.

Alternatively, 'Supply Side' explanations suggest that political disillusionment stems from the failure of political elites to connect with the public, and the failure to engage the masses in politics, i.e it is political institutions themselves that are causing the disaffection. A potential solution for this would be more direct representation through democratic innovations.