The Trafalgar Square Demonstration and Riot of 1886
Sometimes referred to as Black Monday, this brief riot occurred on Monday, February 8, when two rival leftist organizations, the London United Workmen's Committee and H.F. Hyndman's revolutionary Social Democratic Federation, gave notice of their intention to hold meetings simultaneously in Trafalgar Square. Although it was recognized that they might clash violently, there had been no grave public order problems in London since the Hyde Park Riot in 1866, and the British Home Secretary was preoccupied with Irish Home Rule. As a result, authorities did not ordered serious precautions.
The meetings themselves occurred without incident, but when the speakers left the square a crowd of 5000 streamed west along Pall Mall and resumed a fiery meeting in Hyde Park. Due to misinformation, the police believed that there was trouble brewing in The Mall instead of Pall Mall, so they marched away to protect Marlborough House and Buckingham Palace, while a few hundred meters north the mob rushed unhindered along Pall Mall and St James's, famously smashing the local club windows along the way.
