That's my version of the debt as a % of GDP graph (thanks to Kanda for putting me onto the dataset, I should update it again, really - will do soon, the link will update automatically).
Let's just talk through what it shows us.
See that massive spike in the small inset graph, which shows almost a century up to 2008.
That tells us where 1939 to 1945 is.
You can see the steep drop just before that spike as Keynesian policies were tried after austerity had failed ('austerity' and 'trickle down' are both Hooverian terms, used back then).
Then the massive spike in war spending, and then a dramatic post-war drop in the ratio as the benefits of the spending and investment in rebuilding infrastructure put money in peacetime pockets, and it circulated, with a boom in technology and consumer goods, much of it created off the back of both discoveries made but also skills acquired during the war.
Then Thatcher comes along and it gets all bouncy.
Labour inherited a situation that was more or less identical to the one Thatcher inherited and only briefly improved before the impact of her policies bled through. And she had North Sea Oil.
You can see that Brown's attempts to 'abolish boom and bust' (by which I think he did mean a quasi-Keynesian approach of saving in the boom years to spend in the bust) does appear to have flattened the curve, but maybe that is just the effect of artificially suppressing bubbles.
The slight increase just before Northern Rock collapsed is partly North Sea Oil income declining (I think free spirit has posted the graphs for this elsewhere) and also perhaps the first warning signs of a problem in the economy.
The rest is all bankers bailout (direct reported cost so far ~£150bn) and the cost of increased benefits payments and reduced tax take from businesses which have gone bust and workers who have been made unemployed. Because the bankers fucked up.
There is no way you can make the argument that Labour fucked up with high spending. Apart from anything else, in 2007 Osbourne was promising to keep Labour's spending plans in place for three years. They had no problem back then, it is ludicrous to try and claim that it is Labour's fault when they wholeheartedly supported Labour's policy until it all went tits up.