From John Le Carré's Smiley's People:
Suddenly Lacon’s own face took on an appalled expression and his tone dropped to one of near despair.
“You should hear them, George, our new masters! You should hear the way they talk about the Circus! I’m their dog’s-body, damn it; I know, get it every day! Gibes. Suspicion. Mistrust at every turn, even from Ministers who should know better. As if the Circus were some rogue animal outside their comprehension. As if British Intelligence were a sort of wholly owned subsidiary of the Conservative Party. Not their ally at all but some autonomous viper in their socialist nest. The thirties all over again. Do you know, they’re even reviving all that talk about a British Freedom of Information Act on the American pattern? From within the Cabinet? Of open hearings, revelations, all for the public sport? You’d be shocked, George. Pained. Think of the effect such a thing would have on morale alone.
What does "The thirties all over again" mean? What events of the thirties did Lacon refer to? I'm not familiar with British history. Would someone please briefly explain that?