In 2025-26 the United Kingdom spent £96.9 billion on central government net debt interest on the Office for National Statistics measure, and £109.7 billion on the Office for Budget Responsibility measure. The OBR forecasts £137.1 billion by 2030-31. Debt interest is the second largest item of public spending and the only one that funds no public service.
Three things drive the bill. Index-linked gilts stood at £672.7 billion in uplifted nominal value at 31 March 2026, 23.9 per cent of the portfolio, the highest share in the G7 and about twice the next highest. Central bank reserves, which averaged £664.9 billion in 2025-26, earn Bank Rate, so Bank Rate is now the effective interest rate on roughly a quarter of the national debt. And the Asset Purchase Facility, which returned about £124 billion to the Exchequer while Bank Rate sat below the coupons it held, is now indemnified at an estimated lifetime net cost of £164 billion by the end of 2036.
This paper sets out ten measures, models them as a unified plan against the OBR's March 2026 baseline to 2050-51 under five scenarios, states who bears what cost, and drafts the legislation that would be required. Every formula is written out in an appendix and the model is published in full, so the results can be checked rather than taken on trust.
Use of AI tools. The analysis, the model, the figures and the argument in this paper are the author's own. A large language model was used to edit and format Part 11, the draft Bill, so that its structure, numbering and drafting conventions follow those of United Kingdom legislation. No AI tool produced any insight, analysis, interpretation or conclusion, and no AI tool is an author. The author is responsible for the whole of the text.