The 1720 British speculation episode was the South Sea Bubble.
The South Sea Company received a government-backed monopoly over trade with Spanish South America, although its commercial prospects were limited. In 1720, investors were attracted by ambitious claims about the company’s future and by rising share prices. Parliament approved a plan allowing the company to assume part of Britain’s national debt, which further increased public attention.
Shares rose dramatically during the first half of 1720, then fell as confidence weakened and investors tried to sell. The collapse damaged many shareholders and exposed corruption involving politicians and company directors. Parliament investigated the scandal, and several influential figures were punished or disgraced.
The South Sea Bubble is often discussed alongside France’s Mississippi Bubble, which collapsed in the same year. Both episodes helped establish “bubble” as a lasting financial metaphor, although neither was a modern stock-market crash in the later technical sense.