When U.K. Prime Minister Theresa May stalled a crucial House of Commons vote in December because she recognised she might not have the necessary support to push her European Union-Brexit deal through, she hoped the impending 100-day deadline would force more Members of Parliament to back her deal—in desperation rather than through choice.

On Tuesday, her gambit misfired spectacularly. Members of Parliament (MPs) from all parties overwhelmingly voted against the Brexit deal she negotiated with the European Union. The last time a government was so roundly defeated in a Commons vote was in 1924. One MP, Tulip Siddiq, even delayed her planned Caesarian-section so she could vote against the government.

Neil Hodge is a freelance business journalist and photographer based in Nottingham, United Kingdom. He writes on insurance and risk management, corporate governance, internal audit, compliance, and legal...