"No one can know with certainty the future requirements of defence expenditure, for it will be determined by influences largely outside our control. We work only on the basis of rough general considerations. The safest reckoning might be that defence is the one main heading of expenditure which in real terms should not be reduced. Decisions to reduce defence expenditure can be based only on the hope that no one will attack us or our interests or that others will defend us. There are no rational grounds for such a hope, although short-sighted politicians are always tempted to close their eyes to distant dangers of the world as a pretext for spending lavishly on their pet projects. Furthermore, since weapons are certain to become more complicated and expensive, effective defence is likely to cost more and ineffective defence is not worth paying for anyway. Hence it would seem sensible to allow for an increase in expenditure in real terms over the ten years, and the figures in Table 4 accordingly show a rise from £ 3,000 million to £ 3,400 million from 1974-5 after which they are held constant." [This would mean that defence would pass from 10.75% of total public spending to 23.44%]  From "Must History Repeat Itself?"  Churchill Press, 1974.