Coverup by British govt during First World War
Short, easy-to-understand article: https://phys.org/news/2017-08-bank-england-ledgers-reveal-failure.html
War Loan – more information.
At the beginning of the 20th century the national debt stood at around 30 percent of GDP. However, during World War I the British Government was forced to borrow heavily in order to finance the war effort. The national debt increased from £650m in 1914 to £7.4 billion in 1919.
Britain borrowed heavily from the US during World War I, and many loans from this period remain in a curious state of limbo. In 1931, President Herbert Hoover announced a one-year moratorium on war loan repayments from all nations, due to the global economic crisis, but by 1934 Britain still owed the US $4.4bn of World War I debt (about £866m at 1934 exchange rates). Adjusted for inflation, that would amount to around £40bn today, and if adjusted by the growth of British GDP, to about £225 billion. During the Great Depression Britain ceased payments on these loans, but outstanding bonds such as the War Loan were finally paid off in 2015.