But one answer can be glimpsed from a contemporary study, The Rise and Fall of the Great Powers, by Yale historian Paul Kennedy.

CNN: Building On A Golden Age

Reopened two years ago after an extensive renovation, the court contains marble and bronze figurative works by 19th and 20th Century American sculptors like Hiram Powers, Augustus Saint-Gaudens and Paul Manship.

BBC: Celebrating movement amid sculpture

The eminent historian Paul Kennedy wrote a book entitled The Rise and Fall of the Great Powers in which he argued that powerful countries typically undercut their economic strength by trying to control too much territory, leading to their decline.

FORBES: Foreign Policy on a Tighter Budget

He has genuinely taken over many of the decision-making powers previously exercised by the Americans through their now-departed proconsul, Paul Bremer.

ECONOMIST: America and Iraq

If Paul Silk and his colleagues come back this autumn with a recommendation that the Assembly should gain powers to raise more than the "peanut" taxes like the aggregates levy and air passenger duty, then it's Labour who will have the greatest difficulty in accepting much beyond this - and will be the most exposed by being in government.

BBC: State of Play 4 - Labour