BUDGET ANSWERS · SECURITY & PREPAREDNESS
What would 10% more defence spending cost?
Short answer: About £6.6bn a year in extra spending, before anyone changes their behaviour. After five years, the government is borrowing £10.5bn a year more than if nothing had changed, because the economy and debt interest respond too.
The direct cost
We tested raising the defence budget 10% above its planned path in the first Budget and kept it for the whole term. On paper that costs about £6.6bn a year. Cuts affect training and maintenance within six months. Rebuilding starts after a year and takes several years. In a security crisis, shortages increase emergency costs and can cost up to 8 support points, especially after ignored warnings. Global energy inflation affects even well-prepared countries. This models conventional readiness, not removal of the nuclear deterrent.
After five years
Direct costings stop at the first year. The game keeps going: prices, jobs, pay, interest rates and debt interest all respond, and some of the money comes back or leaks away.
| Measure | With the change | No change | Difference |
|---|---|---|---|
| Annual borrowing | £69.5bn | £59.0bn | +£10.5bn |
| Debt as a share of the economy | 96.1% | 95.1% | +1.1 pts |
| Household living standards (index, 100 = today) | 101.31 | 101.35 | −0.04 |
| NHS access (index, 100 = today) | 100.0 | 100.0 | 0.0 |
Ten years on
Ten years on, the model does not judge the country better off than if nothing had changed: on its own, the change is too small to move any measure past the game’s thresholds.
| Measure | With the change | No change | Difference |
|---|---|---|---|
| Household living standards | 102.80 | 102.85 | −0.05 |
| NHS access | 100.0 | 100.0 | 0.0 |
| Housing, transport, justice and schools | 100.0 | 100.0 | 0.0 |
| Military readiness | 108.1 | 100.0 | +8.1 |
| Size of the economy | 99.99 | 100.00 | −0.01 |
| Debt as a share of the economy | 90.0% | 87.5% | +2.5 pts |
Would voters thank you?
Popularity and results are different tests. Here is how each of the game’s three publics would vote with only this change made.
| Public | With the change | No change |
|---|---|---|
| Services & support | 51.5% | 52.0% |
| Lower taxes | 51.5% | 52.0% |
| Mind the books | 51.2% | 52.0% |
How this was worked out
These figures come from the game’s simplified model, anchored to OBR March 2026 fiscal totals, with no external shocks and every other policy left as inherited. They are illustrative, not an official costing. Real outcomes depend on the wider economy and the choices made alongside. Read the model register for sources and assumptions.
In the game you make five Budgets, face a shuffled deck of world events, and are judged twice: by voters on election night and by the country ten years later.