During the War of the Spanish Succession, Britain faced large unpaid government obligations. In September 1711, Parliament and Queen Anne backed a new joint-stock company—the South Sea Company—designed to exchange (convert) parts of the national debt into company shares, so the state could make more predictable payments.
Soon after the charter, the company began taking in government IOUs and paying creditors with South Sea shares of equal face value. This “debt-for-equity” swap made government debt tradable like a stock, creating a fast-growing market for South Sea shares and a new way to refinance public borrowing.
In 1713 the Treaty of Utrecht gave Britain the Asiento de Negros for 30 years—the contract to supply enslaved Africans to Spanish America. The South Sea Company became the main British holder of this right, tying its public story of future profits to the slave trade and limited legal commerce with Spanish colonies.
Even with the Asiento, trade with Spanish America was tightly restricted and heavily taxed, and the company’s real profits did not match public expectations. This gap mattered later, because the company’s rising stock price would depend more on financial engineering and confidence than on steady commercial earnings.
In 1718, King George I took the largely honorary post of governor of the South Sea Company. A monarch’s visible connection boosted public confidence and helped the company present itself as a secure, state-backed enterprise—an important ingredient for later share-price momentum.
In 1719–1720, the South Sea Company proposed taking over a much larger share of the national debt, competing with the Bank of England for this business. Because the company’s profit rose when its shares traded above face value, it had strong incentives to push the stock price higher during the conversion process.
In early 1720 Parliament accepted the company’s plan to assume a large portion of the national debt in exchange for issuing more South Sea stock. This decision linked the company’s fortunes directly to public finance and created the spark for a rapid rise in share prices as investors rushed in.
With the debt deal underway, South Sea shares rose sharply—about £128 in January 1720 to roughly £330 by March. The company expanded demand by offering installment plans and loans secured by its own shares, a feedback loop that could lift prices quickly but also left many buyers exposed if prices fell.
In June 1720, Parliament passed the Bubble Act, restricting unchartered joint-stock companies. The South Sea Company supported this measure; by limiting new competitors, it aimed to concentrate speculative money into established companies like itself, even as the wider market was already overheating.
Speculation reached a high point in late June 1720, when South Sea shares hit around £1,050. By this stage, prices were far above what the company’s trade could plausibly earn, meaning the market depended heavily on continued confidence and the ongoing debt-conversion machine.
By September 1720, confidence cracked and South Sea shares fell rapidly, dragging other investments down with them. The crash spread through the credit system because many purchases had been financed with loans backed by inflated stock prices, so falling prices forced sales and defaults.
In December 1720, Parliament began investigating the company and those linked to it, amid public anger and financial disruption. The inquiries focused on how the scheme was promoted, who benefited from special share deals, and whether corruption and insider advantage shaped the debt-conversion legislation.
In February 1721, a House of Commons “Committee of Secrecy” reported widespread abuses, including bribery and manipulation around share allocations and political support. The scandal damaged leading figures and helped shift political power toward Robert Walpole, who is often described as Britain’s first prime minister.
After the crash, Parliament and ministers took steps to stabilize public credit and punish key insiders, while avoiding a full collapse of the financial system. The South Sea Company was restructured and continued as a debt-management body long after its trading hopes faded, making the bubble a lasting warning about speculation tied to public finance.
South Sea Company and the South Sea Bubble (1711–1720)