That is an interesting graph. However, using spend per head may be slightly misleading.
Between 1983 and 1997 the population increased by roughly 2-3 million. That will clearly affect the figures somewhat.
Now, I accept that the population also increased once Blair took over but let's not forget that his ‘reign’ coincided with an almost permanent state of war on two fronts. Some might say that he had a tiny involvement in that fact.
So, whilst I am not arguing the ‘who spends the most’ point I would be interested to see a graph that shows defence spending in real terms or something similar.
BV