• The victories of federalism over intergovernmentalism from 1950 onwards
• Churchill's early cakeism
• 1973 accession; 1975 referendum and its place in (very sceptical) Lab party politics.
• The 1988 watershed and Bruges.
• ERM and Maastricht (euroscepticism reignited).
• And so on, through to the backstop.
Recommended.
Chapter 1, page 1 of @kevinhorourke's book 'A Short History of Brexit' captures why Brexitism exists.